Abstract:
A musical instrument having a housing. A well is formed in one surface of the housing and adapted to receive a card. A slide is mounted on the housing for movement across the surface of the card. The card containing printed indicia, each of which represents a note of a musical composition with the indicia arranged in a generally rectangular matrix. The indicia on the card are arranged in one direction across the matrix to indicate the sequence of notes played in a musical composition from the beginning to the end thereof. The indicia are arranged in the direction across the matrix extending at right angles to the sequence of playing to indicate changes in frequency of the notes from the lowest frequency on one side of the matrix to the highest frequency on the other side. The slide extends across the card and the well in the direction of the sequence of playing the notes of the composition. The slide is mounted to permit its movement across the face of the card in the direction of change of frequency and the slide can be stopped at any selected position in this direction. An electrical contact is carried by the slide. A plurality of stationary electrical contacts are positioned in the path of movement of the slide contact. The card is indexed so that all of the indicia representing a note of particular frequency aligned with a particular stationary electrical contact so that positioning of the slide over the printed indicia of notes of the same frequency on the card will position the slide contact and a particular stationary frequency contact in electrical engagement. An electronic apparatus is connected to each stationary frequency contact to sound a musical note of a selected frequency when the slide is positioned over the printed indicia on the card representing the notes of that frequency.

Description:
BACKGROUND OF THE INVENTION 
     Present low-cost musical instruments can be classified as blown such as harmonicas, bugles, horns; mechanical such as toy xylophones, toy pianos; electro-mechanical such as toy organs powered by battery and electric motor driven blowers; or electronic such as the Casio Model VL TONE. 
     These instruments display a number of serious disadvantages. Probably the largest single disadvantage common to all these instruments is that in order to play a tune, they require the user to coordinate the motions of multiple body parts, such as fingers, with a score or code showing the sequence of operations needed to produce a tune. Thus, to play the toy piano or the toy organ, the user must strike a series of keys in the proper succession; using multiple fingers if the notes are to smoothly join, and the instructions for this sequence are in the form of notes on a score, or colors on a card, or numbers on a card which in general are physically separated from the keys. Thus, red, or the number 7 must be associated with the striking of a certain key with a certain finger (or covering an air hole, or hitting a bar with a certain hand) and then directly the next code, be it blue or 9 or whatever must be translated to another key struck by another finger or a different fist. These demands on the user&#39;s concentration and physical coordination are difficult and require a period of training even for adults of average dexterity. For children or persons of lesser dexterity, they can be overwhelming. 
     A second major disadvantage of these instruments is the poor quality of the tone produced. Toy or inexpensive instruments do not sound like their real counterparts, and in fact they do not even sound very pleasant, being more noise than music. 
     A third major disadvantage is their inflexibility, such instruments generally having only one mode of play simulating some one real instrument, that instrument being playable in only one of its styles or modes. 
     Those few instruments which add versatility and quality such as the Casio Model VL TONE do so at a vastly increased cost, and in the case of the Casio, considerable difficulties in setting up the instrument and playing it. 
     Another major disadvantage of present instruments is the inability to hold a note while a new note is being selected. 
     A disadvantage of electrical/electronic instruments is the use of failure prone switching, said switching requiring multiple conduction path makes and breaks to select a note or set-up an instrument. 
     Yet another disadvantage is the inability to produce the range of effects necessary to simulate instruments accurately, such as vibrato, tremolo, wow, attack time and decay time. 
     Still another such disadvantage is the inability to produce special effects such as riffles, broken chords, creation of new instrument sounds, automatic note repeat, etc. 
     It has been discovered that all of these disadvantages can be overcome by a novel electronic-mechanical device in which a unique songcard, a mechanical registration method, a mechanical slide coupled to a special array switch, and an electronic circuit are combined. 
     An object of this invention is a musical device which can produce a pleasant tune with continuous note production (sound output), said tune being provided with the instrument on a songboard, when played by a user of only average dexterity, including children, said users being without prior experience or training either on this device or on any musical instrument. 
     One object of this invention is a song annotation in which notes which are linearly connected in the sequence in which they are to be played are also positionally disposed to coincide with that position of the actuating slide which will produce the desired note, such that playing consists of moving a slide along a continuous path pausing at annotated points. 
     Still another object is to produce music of pleasant quality having accurate pitch and good timbre. 
     Yet another object is to simulate a number of different instruments, to allow different modes (such as a glissando mode in which all notes play briefly as they are swept through in going from one sustained note to a different sustained note), to allow instrument groups in which instruments play one-at-a-time alternately, and to allow special effects of many types. 
     One more object is to provide reliable switching in a musical instrument. 
     One additional object is to provide a high quality musical instrument economically priced to qualify as a toy, but with quality and versatility to be of interest to persons of all ages. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is illustrated more or less diagrammatically in the following drawings wherein: 
     FIG. 1 is a top plan view of a musical instrument embodying the novel features of this invention; 
     FIG. 2 is an end elevational view of the musical instrument of FIG. 1; 
     FIG. 3 is a side elevational view of the musical instrument of FIG. 1 on an enlarged scale with portions broken away and others shown in cross section; 
     FIG. 4 is an enlarged cross-sectional view taken along line 4--4 of FIG. 1; 
     FIG. 5 is a top plan view of a note card; 
     FIG. 6 is a schematic view of the slide switch contacts; and 
     FIG. 7 is a schematic view of the electronic circuitry of the musical instrument. 
    
    
     GENERAL DESCRIPTION OF THE INVENTION 
     The novel solution to the foregoing problems and the realization of the aforementioned objectives has been achieved by combining a songcard, a slide coupled to an array switch, a housing which registers the songcard, the slide, and the array switch with reference to each other, a digital state machine which responds to the switch array and several auxiliary switches to produce outputs which through several transistors, resistors and capacitors, and diodes drive a loudspeaker. 
     The songcard is a generally rectangular piece of paper or cardstock on which the notes are printed as symbols such as circles or dots, each in a left-right position corresponding to pitch and in an up-down position corresponding generally to sequence of play, said notes being linked in sequence of play by a printed line which will in general define a serpentine pathway from start to end of a song. This arrangement of symbols can also be referred to as a matrix of columns and rows. The note annotations are generally varied for duration, the words may be printed below the notes, and other instructions such as instruments recommended or tempo and various art may be printed on the songcard. The edges of the songcard register with the walls of a well provided on the housing. A slide moves along this well, supported by the housing. A printed circuit board, registered to the housing in any conventional manner such as by bolts extending through the board and into bosses onto the housing bears a switching array which is also registered to the housing and thus to the songcard. An electrical contact carried by the slide contacts the switch array on the printed circuit board. Thus, when the note position and slide are in coincidence, the electrical contact of the slide is at a known point on the switch array where it will call for the appropriate note from the digital state machine. The output of the digital state machine is translated to music by the other components and the loudspeaker. 
     Only a single hand of the player is needed to move left and right registering the cursor line on the slide with each note in turn as the player&#39;s eye follows the continuous interconnecting path from note to note. 
     As the slide moves, thus moving its electrical contact, it operates two related but electrically isolated switching circuits. The &#34;A&#34; circuit makes a single closure at a time, closing one of three driven busses to one of seven input lines, for a total of 21 possible positions. Since only a single closure is made, there is no switching skew problem and there is no debounce problem. If a closure is sensed, then it constitutes a proper code. If no closure is sensed, then the digital state machine keeps searching for one. 
     The &#34;B&#34; circuit is a single closure which occurs before the &#34;A&#34; circuit changes state (or opens) and which reopens after the new &#34;A&#34; state is established. The function of the &#34;B&#34; closure and reopen is to signal the &#34;A&#34; change of state. 
     The device has a choice of two modes: 
     In mode one, an established note will continue until there has been a closure and reopen on &#34;B&#34; followed by a period with no further activity on &#34;B&#34;. Thus, if the slide is on note five, and note five is established and playing, and the slide is moved toward higher notes rapidly, note five will continue playing until the slide stops and rests. Circuit &#34;B&#34; will now show a lack of activity, and will be open, assuming the slide is at a note position, and a new note will be established. The intervening notes were never established because there was not a sufficiently long period of inactivity on the &#34;B&#34; circuit. This novel arrangement allows the playing of widely separated notes without a corresponding time gap between the sounding of the notes, and without the sounding of the intervening notes. In mode two, a new note is established directly upon the reopening of the &#34;B&#34; circuit. Thus, the sounds are contiguous in a temporal sense, and all intervening notes play producing a glissando. The choice of modes is controlled by a switch which communicates a signal of one bit to the digital state machine. 
     The positions of the slide are normally interpreted as notes. There are twenty-one note positions plus a position at one far end for which no &#34;A&#34; circuit closure occurs. This position is silent, producing a rest. A closure of a momentary &#34;SET&#34; switch transmits one bit to the digital state machine, causing it to interpret the then slide position as an instrument setting position. Sixteen of the twenty-one note positions are so double used, corresponding to eleven traditional instruments (xylophone, cello, mandolin, bass, guitar, piano, violin, harpsichord, organ, clarinet and banjo), three special effects, and two orchestra positions. Any of these sixteen choices can be made at any time by positioning the slide to the desired position and momentarily actuating the slide to the desired position and momentarily actuating the &#34;SET&#34; switch. 
     The orchestra positions are a novel feature in a musical instrument or device. Each consists of a set of four instruments. These instruments play cyclically. When orchestra is selected, notes will play in the voice of instrument one of the orchestra group. When the &#34;NEW INSTRUMENT&#34; switch is momentarily closed, transmitting a bit to the digital state machine, then the next note to be played will be in the voice of instrument two of the selected orchestra group. Three follows two and four follows three similarly. Next, one follows four, etc. Each closure of the &#34;NEW INSTRUMENT&#34; switch causing an instrument change to occur on the next note to be played. This preset feature is also novel and allows the instrument change to occur in a smooth fashion without demanding coordination on the part of the user. 
     Thus, the input information of the digital state machine consists of the &#34;A&#34; and &#34;B&#34; circuits, the &#34;SET&#34; bit, the &#34;GLISS&#34; bit, and the &#34;NEW INSTRUMENT&#34; bit. 
     Four output bits from the digital state machine drive a four-bit digital-to-analog convertor which is followed by a capacitor which both sets attack and decay in conjuction with the four-bit digital-to-analog convertor and acts as a low-pass filter in conjuction with a resistor. A fifth output bit overrides the limited attack rate of the digital-to-analog convertor and forces an almost immediate attack to full amplitude (for example for a piano sound). A sixth output bit overrides the previous five bits and forces the function to zero thus immediately stopping the sound (abrupt halt). The six output bits together establish the sound envelope. 
     Two additional output bits, weighted two-to-one, modulate the envelope at an audio rate or rates established by the digital state machine. This audio signal is current amplified by three emitter followers and applied to a speaker. 
     Three additional outputs from the digital state machine drive a three-bit digital-to-analog convertor, the output of which is integrated and applied through a resistor to the RC (resistor-capacitor) clock which operates the digital state machine. Thus, the state of these three outputs of the digital state machine determines the clock rate of the digital state machine. The clock rate in turn determines the pitch of the note. The higher the clock rate, the higher the pitch of the note. The integration is essential, both for musical reasons, and to prevent abrupt clock changes which could disorganize the digital state machine. The function of this circuit is to provide vibrato and other changing frequency effects. The integration smooths the inherent step functions in the digital output and makes for a pleasing vibrato. 
     The six envelope control bits, in addition to controlling attack time and decay time, produce silence, wow (amplitude oscillations), tremulo (combined with the frequency control bits), etc. 
     The two audio rate bits control the basic pitch of the note, the amplitude (by operating both bits, the low-weighted bit only, or the high-weighted bit only), and the timbre of the note by operating the bits in a cyclic pattern with internal structure. The pattern repetition rate determines the pitch and the pattern structure determines the timbre of the note. 
     An instrument is simulated by selecting appropriate behavior for the envelope control bits (thus for a piano, immediate full amplitude attack, and medium decay to zero), for the frequency control bits (for a piano, fixed frequency-no vibrato, etc.), and for the audio rate bits (modest timbre structure for the piano). Additionally, the frequency range is adjusted for the instrument selected. Thus, the twenty-one note range is different for different instruments. As another example, the violin has a moderate starting amplitude which swells to full amplitude, moderate vibrato, no decay (continuous tone production), a pure voice (no internal structure), and a high pitch range. 
     The various instruments are represented as tables in the digital state machine, the proper table entries being called-up by an instrument &#34;SET&#34; or &#34;NEW INSTRUMENT&#34;. 
     The required digital state machine could of course be realized by assembling sufficient counters, registers, logic gates, etc., and organizing them into high speed functional groupings each dedicated to one of the tasks required, such as operating the audio rate outputs, operating the frequency control outputs, operating the envelope control outputs, reading the &#34;A&#34; circuit, monitoring the &#34;B&#34; circuit, monitoring the &#34;SET&#34; bit, monitoring the &#34;GLISS&#34; bit, or monitoring the &#34;NEW INSTRUMENT&#34; bit. 
     It has been discovered that the very high rates necessary to produce audio output can be reached with a single set of hardware which can also perform all of the other required functions without ceasing the production of audio or changing the pitch of the produced audio by properly organizing the digital state machine. The requisite organization, an organization unique to electronic music devices, is to produce a portion of the time delay which corresponds to the shortest unit time in the audio pattern being produced, to produce the next output state from the cyclical output table, then to jump to the next task of a list of tasks and perform that task, then having advanced the task counter and the output state counter to repeat the cycle. The tasks must be of constant time length, all equal, and this must be true regardless of execution path through the task, a requirement which is met with a series of time delays. This fixed part length adds to the variable time delay to determine the pitch (through the unit pattern length). The fixed path length through the tasks added to the minimum length through the variable note delay determines the shortest delay and thus the highest pitch producible. 
     There are many combinations of hardware which could realize the foregoing organization and thus be used to construct this device. However, for economy and simplicity, a preferred embodiment uses a National Semiconductor Microprocessor, COP421, with options according to Table I and ROM values according to Table II. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1 to 3 of the drawings show a hollow housing 11 conveniently formed of top and bottom plastic sections 13 and 15 respectively which may be fastened to each other in any conventional manner. The housing is relatively flat and rectangular in shape and has a handle opening 17 formed at one end thereof. A depressed well 19 of generally rectangular shape is formed on the upper surface of the top housing section 13 and is adapted to receive and register a songcard 21 (shown in FIG. 5) relative to the housing. A slide 23 is mounted on the housing and is adapted to be moved across the depressed well 19 in the directions shown by the arrows in FIG. 2. The slide is preferably formed of a transparent material and has a guide line 25 formed thereon. One end of the slide has a U-shaped clamp 27 fastened thereto which clamps fits over the edge of the housing in the manner shown in FIG. 3. A support 29 for electrical contacts 31 and 33 (shown in FIGS. 3 and 6) is attached to the opposite end of the slide and extends into the interior of the housing 11 where the contacts can be moved along the lengths of the stationary electrical contacts 35, 37 and 39 of the &#34;A&#34; circuit and 41 and 73 of the &#34;B&#34; circuit which form part of the switching array and are shown in FIGS. 6 and 7. These circuits may be conveniently formed on the surfaces of a printed circuit board (not shown) which is positioned in the housing in alignment with the path of travel of the slide electrical contacts support 29. 
     Cantilevered finger operated levers 42 and 43 are molded in the top section 13 of the housing 11. As shown in detail for lever 42 in FIG. 4, each lever has a finger engaging button 45 on its upper surface and a downwardly extending leg 47 which engages a momentarily actuable switch, preferably a laminated plastic electric switch, which is not shown other than in the schematic of FIG. 7. Slidable handles 49 and 51 are mounted on the top section 13 of the housing and are used to operate electrical switches of the instrument which are shown in the schematic of FIG. 7. 
     A grill 53 shown in FIGS. 1 and 4 is formed in the top section 13 of the housing 11 and provides openings into the interior of the housing to permit the escape of heat and sound therefrom. An irregularly shaped raised surface 55 shown in FIG. 3 is located along one side of the tip section of the housing beneath one end of the slide 23 and is adapted to receive a decal 56 shown in FIG. 6 which identifies special effects which may be obtained at various positions of the slide and the switch functions for lever 42 and handle 49. 
     A songcard 21 is shown somewhat schematically in FIG. 5. Printed on a surface of the songcard, which may be made of card stock, heavy paper or plastic, are a start position 57 and an &#34;off&#34; or &#34;end &#34; position 59 connected by a printed trace line 61. The start and end positions are located on one side of the songcard in alignment with each other relative to the slide guide line 25. The trace line connects notes 63 which are printed on the songcard. The notes may be of different shapes such as circles or dots or even colors to indicate different durations, etc. but all notes of the same frequency will be positioned so that they will be aligned with the slide guide 25. The notes will vary in frequency from the left hand side of the songcard to the right hand side as shown in the drawings. Printed instructions, art work and words for the songs may also be printed on the songcards but are not shown in the drawing for clarity of illustration. 
     The alignment of the stationary electrical contacts of the array circuits A and B with the instruments and other effects listed on the decal 56 and the columns of indicia 63 representing notes of different frequencies on the songcards 21 is dispicted in FIGS. 5 and 6 of the drawings. For example, when the guide line 25 of the slide 23 is aligned with the indicia on decal 56 labeled &#34;Special Effects 2&#34; and with a column of indicia 63 on the songcard, it is aligned with one of the stationary electrical contacts of path 39 of array circuit A. The movable electrical contact 31 of the slide is in electrical engagement with this stationary contact. For convenience of illustration, this alignment is shown by reference line C in FIGS. 5 and 6. Normally, the notes indicated by the indicia 63 on the songcard will be played. However, if lever 43 has been actuated to close switch 165 (hereinafter described) the notes will be played in the voice of special effects 2. 
     The array circuits A and B and the circuitry connecting these circuits to a power source 65, a digital state machine 67 and a loudspeaker 69 are shown in FIGS. 6 and 7. The power source 65 consists of five AA batteries arranged in series to provide a 7.5 volt DC output. An on/off switch 71 operated by slidable handle 51 is connected to the negative side of the power source and to the common ground connector 73. 
     The digital state machine 67 includes a microprocessor 75. A suitable microprocessor is a COP421 manufactured by National Semiconductor Corp. of Santa Clara, Calif. and further described in their bulletin COP420/421 Single-Chip N-Channel Microcontrollers. This microprocessor has 24 pins or leads numbered 1 through 24. Lead 1 is a ground lead and connects to the common 73 of the device circuit, symbolized by 0 V (zero volts, therefore the potential reference point for all circuit voltages). This circuit common 73 connects to the negative most lead 77a of the 5 AA cells 65 through on/off switch 71. The positive most lead 77b of the 5 AA cells 65 connects to 1/2 amp silicon power diode 79, which offers protection against damage from accidental polarity reversal, to positive supply bus 81. Capacitor 83, an aluminum electrolytic 100 microfarad capacitor rated at 10 working volts connects between buses 81 and 73 providing power supply decoupling and filtering. 
     Transistor 84, a Motorola MPS2222, drives speaker 69 through external speaker jack plug 85 via connecting leads 87 and 89. Plugging an external speaker into jack plug 85 disconnects speaker 69 and transfers the output to the external speaker. Transistor 91, a Motorola MPSA20, drives transistor 84. Resistor 93, 4700 ohms, acts as a base return for 84. Transistor 95, a Motorola MPSA70 PNP drives transistor 91 with 10 kilohm resistor 97 acting as an emitter load for transistor 95. All three transistors are connected as emitter followers, and act to transform the 8 ohm impedance of speaker 69 to a value in the several hundred thousand ohm region. 
     Capacitor 99, preferably a 0.0033 microfarad ceramic or polyester, and resistor 101, preferably a 47 kilohm resistor, connect in series from the base of transistor 95 to the 0 V buss 73, act to modify the frequency response of the amplifier system for a more pleasant sound. Resistors 103 and 105 adjust both the amplitude and voltage offset at the input to the amplifier comprising 95, 91, 84 and associated parts, so as to obtain linear amplitude performance. Voltage on conductor 107 is applied to 10 kilohm resistors 109 and 111 which connect respectively to 220 kilohm resistor 113 and 100 kilohm resistor 115. The voltage at 117, the base of transistor 95 will depend on the voltage applied to 107 and the states of the microprocessor output on 75-pin 24 also called D0 which connects to the junction of 111 and 115 and is an open collector (sinking) output, and the output on 75-pin 23 also called D1 which connects to the junction of 109 and 113 and is similarly open collector (sinking). When these outputs are on (conducting), the voltage at 117 is the offset voltage established by 103 and 105. When either output is off (non-conducting), its respective resistor branch contributes a current proportional to the voltage at 107 thus creating a voltage at 117 which drives speaker 69. When D0 and D1 switch on and off at audio rates, the speaker 69 is driven at those audio frequencies. Thus, one or two basic audio pulse rates are possible since D0 and D1 can have different switching rates, and three different drive amplitudes are possible for any given voltage at 107 since the two branches have differing resistors. Stated another way, the microprocessor output ports D0 and D1 establish the audio waveform. 
     Since the audio drive is proportional to the voltage at 107, this voltage establishes the audio envelope (attack, amplitude, and decay, etc.) Resistors 119, 121, 123 and 125 of values 100 kilohms, 220 kilohms, 470 kilohms and 1 megohm respectively, and connected to microprocessor ports L7 75-pin 5, L6 75-pin 6, L5 75-pin 7 and L4 75-pin 8, respectively, form a 4-bit DAC (digital-to-analog convertor). The voltage at common point 127 will be a function of the input state to this DAC. Conductor 129 connects common point 127 to microprocessor port D3 75-pin 21. This open collector (sinking) output port when conducting will override the DAC output, forcing the voltage at 127 to zero and silencing the output from the speaker. Conductor 131 connects microprocessor output port D2 75-pin 22 to common point 127 through 1N914 type diode 133. When open collector (sinking) output D2 is off, resistor 135 applies current from positive buss 81 to common point 127 through diode 133, overriding the DAC and causing full output from 127. 4.7 kilohm resistor 137 and capacitor 139 of value 0.22 microfarads and preferably polyester, form a low pass filter to stop extreme transients from reaching the base of transistor 141, a Motoroal MPSA20. Transistor 141 and its emitter load 143, a 10 kilohm resistor, act as an emitter follower to transfer the voltage from the filter 137-139 to line 107. Thus, the audio waveform envelope is determined by the states at microprocessor ports D2, D3, L4, L5, L6 and L7. D3 conducting (logic zero) turning all sound off (immediate cutoff) and overriding the other ports, D2 turning sound full on at an attack rate limited by 135, 137 and 139, and overriding all except D3, and L4, L5, L6, and L7 establishing attack rate, decay rate, and amplitude provided D2 is conducting (logic zero) and D3 is non-conducting (logic one). 
     Microprocessor 75 has a clock rate which is established by 10 kilohm resistor 145 connected from positive bus 81 to clock input pin (also called CKI) 75-pin 3 and 100 picofarad capacitor 147, ceramic, mica, or polyester, connected from CKI pin 75-pin 3 to 0 V bus 73. This clock rate is modified (modulated) by current flowing through 47 kilohm resistor 149 connected from 75-pin 3 to the common point 151 to a DAC consisting of 47 kilohm resistor 153, 100 kilohm resistor 155 and 220 kilohm resistor 157, driven respectively by microprocessor ports L3 75-pin 10, L2 75-pin 11, and L1 75-pin 12. A 2.2 microfarad aluminum electrolytic capacitor 159 connects from the common point of the DAC 151 to 0 V bus 73 and thus filters the voltage at 151 causing the frequency modulation of the microprocessor clock to be substantially triangular with time (approximately linear frequency versus time). This modulation of the microprocessor clock will in turn time modulate all internal processes and thus all microprocessor produced signals providing such effects as vibrato. 
     75-pin 9 is the Vcc input for the microprocessor and connects to positive buss 81 as does reset pin 75-pin 4. Clock output CKO 75-pin 2 and SI input port 75-pin 14 are not used. 
     Port G3 75-pin 20 is used as an input and connects to bus 73 through switch 161 operated by lever 41 signalling the microprocessor to produce either notes selected by pausing the selector, or all notes passed over by the selector (glissando). 
     Port G2 75-pin 19 is used as an input and connects to bus 73 through switch 163 operated by slidable handle 49 which signals the microprocessor to change to a new instrument simulation by being momentarily closed. This feature is used in conjuction with the orchestra feature. 
     Port L0 75-pin 13 is used as an input and connects to bus 73 through switch 165 operated by lever 43 which signals the microprocessor to select (set) an instrument to be simulated by being momentarily closed. 
     Ports G1, SK, and S0, 75-pin 18, 75-pin 16, and 75-pin 15 respectively are used as outputs to drive (scan) switch contacts 31 and conductors 39, 37 and 35 respectively, all of which are parts of the array switch. Ports L1 through L7 75-pins (12, 11, 10, 8, 7, 6, 5 respectively) are used as inputs from scan lines 39, 37 and 35. The electrical contact 31 of the slide 23 engages one of the stationary contacts 35, 37 or 39 and one of the stationary contacts 166 which is connected to a particular one of pins 5, 6, 7, 8, 10, 11 or 12. This 3-to-7 switch array has 21 possible single contact states which are established by the position of the slide contact 31, each state representing either a note or an instrument selection, depending on the state of switch 165. A closure of switch 165 selects an instrument (or orchestra instrument group) based on the position of the slide contact. If switch 165 is open, then the slide contact 31 selects notes. 
     Port G0 75-pin 17 is used as an input and connects to bus 73. As slide contact 31 moves between selection positions, contact 33 momentarily connects buss 41 to bus 73, signalling the microprocessor 75 that a new selection of note will shortly occur. Capacitor 167 connects from bus 41 to bus 73 and has a value of 2.2 microfarads. This capacitor insures that the bus 41 will remain at a low voltage long enough for the microprocessor to record it. 
     Resistor 169 protects the internal circuit in case of a short in an external speaker, and has a preferred value of 22 ohms. 
     A typical operating program for microprocessor 75 is located at the end of this specification. An explanation of this program identified by line number is as follows: 
     The program source code is written in National Semi-Conductor&#39;s macro-assembler language for its COP421 microprocessor. 
     Lines 1-5 instruct the assembler as to title, printing instructions, chip (microprocessor) type, and force a noassemble condition for the following blocks lines 19-169 (an alternative to line-by-line comment symbols). 
     Lines 19-33 include a brief description of the hardware. 
     Lines 36-39 adapt the code to either an old (oldpc=1) or new (oldpc=0) pc board layout. Final product uses the new layout, thus oldpc=0. This selection affects lines 153 through 169 which provides two alternative sets of assignments depending on pc layout. 
     Lines 41 through 110 assign names to the various RAM cells of the COP 421. These cells can then be referred to in the assembly code by name. 
     Lines 113 through 150 similarly assign a variety of names for convenience in writing assembly code. 
     Lines 171 through 183 constitute a macro which does the manipulation necessary to prepare a &#34;voice&#34; table. 
     Lines 187 through 199 start the code proper. These lines clear the RAM to all 0&#39;s. 
     Lines 632 through 765 and 953-961 initialize the parameters which cause the music to have the characteristics of a specific instrument. 632-649 are common to all instruments. 650-653 do an indirect jump based on the contents of the LEVAL RAM cell (Low Evaluation). The jump will go to an instrument such as Violin (line 655) or Cello (line 667) with the table at 539-555 controlling the jump destination. 
     The parameters dealt with include Amplitude, Swell, Decay, Vibrato, Staccato, Wow, Voice, Pitch, and Special Effects. 
     After setting the instrument by initializing the appropriate RAM cell values, the code jumps to DSNG lines 202-236, 851-857, 923-927, and 950-952. The first time through, this code plays a little `song` in the voice of the first instrument (piano). The song is stored at the song table 919-921. After playing the song, this code sets SNGCNT to cause future passes to skip playing the song. 
     Lines 240-268 read a note from the keyboard. SLDCNT is a RAM counter telling time elapsed since the slide moved to a new note. It controls the transition to a new note. RDNT clears this nibble of RAM and then reads the keyboard (subroutine RDKB). 250 tests the Glissando bit (input G3) to control the between notes delay (sub DLYMAX). 255-256 clear the elapsed time register (LELPTM/HELPTM) which keeps track of time since last note was changed and cause return to the song after an interval to protect against battery exhaustion due to the player forgetting the unit is turned on. 258-260 clear a RAM timer. 262-267 handle the change of instruments in orchestra mode, along with 1388 through 1402. 
     Lines 271 through 338, and 1364 through 1382 set the parameters needed to produce a new note. These include the base pitch from which the note pitch will be calculated (278-289), the special effects mechanism which utilizes an ESCAPE nibble and manipulates BPITCH according to a table at lines 774 through 783 which is read by the sub at lines 795-797, said special effects being setup by 290 through 301, the decay and swell mechanisms handled by lines 302-329, the establishment of the new note value handled by 330 through 338 and 1364 through 1372 which call the sub STNDL (set tone delay) at lines 889 through 910. This sub reads the note table at 866 through 883. Finally 1373 through 1382 set pointers to the voice table which is located at 936 through 949 and establishes the output waveform and thus the timbre. 
     Lines 339 through 531 are the subroutine pages and include math subroutines (complement, add, subtract, etc.), delay subroutines which insert instructions to cause time delay to equalize the running times through various paths to prevent jitter in the note production, and specialized subroutines. Notice that the DLY 13   subs chain for word usage efficiency. The JSD 13   subs do a delay and then go to SPKOUT instead of doing a subroutine return. These subs are used as equalizers in the note production path and not as general purpose delays. They use the subroutine mechanism as an efficiency convenience (one-byte call) and not as a true subroutine. This is a novel feature of this program. PRRDL (441-442, 471-475, and 486-491) prepares for a read of the L port. RDLP (444-445, 476-491) reads the L port. These subs return through a delay for word usage efficiency only. EVBY (447-449 and 494 through 517) evaluates the L port read by reducing the input image which has been read into a byte of RAM to a number in a nibble. The subroutine RDKB at lines 557-602 does all portions of the keyboard read and evaluation, calling subs to clear the receiving nibble, prepare to read the L port, setting the keyboard strobe (SO, SK, or G1), calling sub to read L, and evaluating the resulting byte. Since the keyboard is based on only one closure per note, the first closure ends the read. If no closure is found, the read routine loops and continues looking (line 586). When RLRDKB RAM register overflows, the loop terminates by jumping to MREST (rest), lines 603-611 which set DMASK to O to silence the sound and then jump to the sound producing loop (which will now however be silent) which loop monitors slide for signs of activity. 
     The sound producing loop begins at 966. Lines 966 through 993 produce an output at the D port to create the desired audio waveform in accordance with the VOICE table and produce an output at the L port to drive the amplitude and frequency modulation DAC&#39;s. (DAC=Digital-to-analog convertor). The code continues with 999 through 1018 which is a time delay generator and produces a delay in accordance with the note value desired thus setting the time around the loop and the pitch. This delay scheme uses a delay sub DLY251 at 1341 through 1353 and a delay sub DELA11 at 1359 through 1362. The tone delay exits to L1ML at 1064. TMFLGS, a RAM flag controls the flow to either TIMER or TASK. As long as the flag is one, the flow is to TIMER, at 1023, where a real time clock is tested (SKT) and if expired, then the real time timer nibbles in RAM (LTIMER, HTIMER) are updated and the TMFLGS Is set for task. At each pass through the timer GO is tested to see if the slide has moved. If the slide is Low (GO low) then SLDCNT is set to 1. If the slide is up (GO high) SLDCNT is tested. If it was zero, no change is made (GO must go low before SLDCNT can advance). If it was one, it is set to two. If it was two or more, it is left as was. In Glissando mode, if the count is two or more, the timer goes to DSNG to begin a new keyboard read. Otherwise, timer exits to SPKOUT for another loop. 
     If ML goes to DO TASK, then the program will jump through a task table, based on the contents of LTIMER the real time timer. Thus each real time advance returns the flow through DO TASK and causes the next task to execute. In between tasks the flow is through TIMER waiting for the real time clock. Because of this, the tasks execute at a fixed rate regardless of the note pitch (the rate of the loop being inversely proportional to the pitch). 
     Lines 1073 and 1074 cause the jump through the table at 1082 through 1086. Not all of the jumps are normally used. There are sixteen jump designations in four lines and the LTIMER accesses them in order as it goes from 0 through 15, but task SERT (service timer) resets the timer to 2, so the last two SERT tasks would not normally be reached nor would the leading two SERTS. 
     ELPT 1140 through 1151 advances the elapsed timer to operate the warning tune is the instrument is left unused but with power on. 
     SWLL 1203 through 1231 operates the swell mechanism causing the sound to swell from said initial value to full amplitude at some rate, provided swell is called for based on the INIT. 
     If WOW is called for, WWOW 1237-1247 causes the amplitude to wow up and down. 
     TELP 1267-1283 tests the elapsed timer and if it overflows jumps to START causing the initial song to play and warning the user that power is still on. 
     VIBR 1104-1115 operates the vibrato if called for. 
     If decay is called for DDEC 1119-1138 provides it, causing the amplitude to decay at some rate. 
     Note: Vibrato is a linear up and down frequency modulation. 
     RDLS reads the L port into LLIN, 1091-1095. 
     TSLS 1172-1180 tests for a call for new instrument. If LO was read in low into LLIN lines 1177-1180 jump to DSET 613-631, which reads the keyboard for the new instrument information and goes to INIT. If G2 is low lines 1173-1176 set a memory flag and if in orchestra mode than an instrument change will occur on the next new note. 
     SLDC 1185-1200 tests slide count, (RAM cell SLDCNT) and if it is not equal to zero advances it. If it overflows, the program branches to DSNG and a new note. 
     TESC 1255-1264 tests HTIMER and ESCAPE and escapes the loop to DESC for special effects. 
     SNGE 1330-1339 does special effects during the initial song. 
     SERT 1319-1327 services the timer, advancing HTIMER and resetting LTIMER. 
     DESC lines 799 through 850, and 1284 through 1314 create the special effects such as ping-ponging between two notes, producing a short lead note, producing a twang in front of a note, and producing a cascade of notes up or down the scale. 
     The foregoing program may be modified if the production microprocessors vary from the prototype. 
     While the foregoing describes a preferred embodiment, many other embodiments within the spirit of the invention will be obvious to those skilled in the art. ##SPC1## ##SPC2## ##SPC3## ##SPC4##