Patent GB-1137516-A (GB)
Title: Improvements in or relating to electrical musical instruments
Inventor: STINSON HERMAN BIRCHARD
IPC: G10B3/10
Filed: 1966-03-17
Abstract: 1,137,516. Electrical musical instrument. CHICAGO MUSICAL INSTRUMENT CO. 17 March, 1966, No. 11775/66. Heading G5J. As a musician plays a melody on one keyboard or section of keyboard of an electrophonic or electrically operated musical instrument, such as an electrical pianoforte, organ or accordion, with one hand, and an accompaniment with the other hand on another keyboard or section of keyboard, automatic fill-in means are used to add to the octave below the melody notes actually played with the one hand, further notes selected by the playing of the accompaniment with the other hand. These fill-in notes may be varied in amplitude relative to those of the melody and accompaniment and notes in different ranges may be made to have different voices so that together the melody, accompaniment and fill-in notes produce complex effects, such as that of a string quartet playing in harmony. When melody keys 25 are played actuator bars 35, associated one with each of them, act each to close those of a series of switches 33, associated one with each melody key 25, which correspond to notes in the octave immediately below the key played. The switches 33 are individually connected to a series of switches 30, associated one with each accompaniment key 26, by lines 34 and it is only if the appropriate accompaniment key 26 is played and its associated switch 30 in consequence closed, and its controlling switch 36 in the common line 31 is closed, that a complete circuit exists and a signal from the appropriate tone source 20 passes through switches 33 and 30 to the output. The melody note is sounded in consequence of the closing of switch 27 by key 25, the accompaniment one through the closing of switch 28 by key 26 and a note in the octave below the melody one as a result of the completion of the above circuit. When a chord is played on the accompaniment keys at the same time as a single melody note, a number of notes in the octave below the melody note sound also, due to the closing of switches 33 and 30, the added notes corresponding in name to those of the accompaniment. Accidental actuation of notes an octave below the higher notes played through lines 34a when three or more keys of the melody keyboard are played together and switch 36 is open may be avoided by replacing the switches 27 with double-throw switches 39, connected as in Fig. 6. Where a sustaining device, such as an earthed capacitor 51 connected through a switch 52 to a tone signal source 40, is used undesired coupling can take place, through switches 30, when the switch 48 is open, and may be prevented by including an electronic switch or glow tube 53 in each line line 34, as in Fig. 6. Two tubes 53 have a combined ignition voltage which is higher than the sustaining voltage across the capacitor 51. Rather than have actuator bars which extend to one side of the keys T-shaped ones may be employed, and the melody key positioned relative to the closed switches by shifting the melody key switches 27 to the left or the fill-in switches 33 to the right. Alternatively each melody key 25 may be provided with (say) nine fill-in switches and with an actuator bar which simultaneously closes a series of the switches corresponding to notes in the octave below the melody key. The movable element of each of these switches is engageable with a bus common with up to nine adjacent switches each corresponding to a note. When the control switch is closed playing of (say) key C7 closes the nine switches associated with it and when accompaniment keys are simultaneously depressed a potential is brought to such of the lines 34 as have corresponding keys 26 depressed and switches 30 closed. This potential is sufficient to cause electronic switches 53 in the circuits to ignite and the potential passes through the appropriate closed note-related switches and lines 34 to activate the tone signal sources 40. If space requirements prevent the use of mechanically-actuated multiple switches in this way the actuator bars may be replaced by stacks of switches operated by a solenoid, energized by the closing of a switch operated by the key 25. In another embodiment the accompaniment keys and actuator bars close switches in a power circuit, energizing solenoids which operate the keys corresponding to the fill-in notes. In this version a conventional piano action or other non-electrophonic tone-producing means may be employed. Stack - switches may be used in place of actuator bars to delineate a group of solenoids corresponding to notes in the octave below the played melody notes and with movable armatures connected to the keys 25 or to associated switches 27. Rectifiers or diodes prevent undesired coupling. Each key 25 controls a switch 27, or tone-producing means, and a movable element of a normally-closed switch, associated with a note three notes lower, whose engaged contact is connected through a further normally-closed switch to the movable element corresponding to the nexthigher note. Each of the last-mentioned switches is under the mechanical control of a key 25 located eight notes higher and when the key is depressed the switch opens, breaking the continuous series circuit and isolating the solenoids an octave or more below the played key. Simultaneous opening of other switches isolates the solenoids from two notes below the played key and upwards and closing of alternative contacts connects leads to the appropriate solenoids so that they may operate if power is brought to them through lines 34. The electronic switches may be omitted from the instrument and undesired coupling be prevented by use of multiple switches with each accompaniment key, together with a rotatable bus which acts as an on-off switch, each of the multiple switches being connected to an appropriate line 34. The bus has a conductive side and an insulating one and may be rotated by a crank, so that an appropriate side is contacted by the movable elements of the multiple switches. Alternatively the bus may be displaced laterally or the movable elements of the multiple switches displaced so that they cannot contact the bus.