Patent GB-1021212-A (GB)
Title: Rhythm tempo control system
IPC: G10H1/42
Filed: 1963-08-15
Abstract: 1,021,212. Electrophonic musical instruments. SEEBURG CORPORATION. Aug. 15, 1963, No. 32260/63. Heading G5J. In an electronic musical instrument of the continuous repetitive rhythm type used to accompany a principal instrument under player control e.g. an electrical organ, the continuous repetitive rhythm and the tempo in which it is played are derived from a fixed pattern of a commutator, the speed of the brush member of, which being controlled so that the tempo of the repetitive rhythm follows the tempo at which the principal instrument is operated by the player. In the general arrangement, Fig. 1 (not shown), a rhythm sequence is derived from a commutator and code matrix unit 31, the commutator being driven by a D.C. variable-speed motor 32. Output leads 33 and the supply and control leads are connected to control panel 35 which provides a manually operable rhythm selector switch 36, a volume control 37 which is combined with an on-off switch for the rhythm section, and a tempo control 38 which is combined with an automatic-manual switch. Tone generator 41 generates eight different kinds of rhythm tones in the sequence corresponding to the applied input pulses at terminals 42. Volume control 37 supplies the rhythm pulse tones to output 39 which applies the tone signals to the organ voicing assembly. For novelty effects an optional " beat-box " unit 48 may be provided with manually operable switches 49, each of which supplies an input to one of the tone generators in the unit 41. A motor control circuit 51 receives a phase signal on line 52 from the commutator and a pedal switch signal on line 53 from the organ operated by the player, which is related to the tempo at which he is playing, and supplies a control current to the motor 32 for determining the speed of rotation of the motor 32 and thus serves to control the tempo of the rhythm pattern generated by the commutator and code matrix. Fig. 2 shows the circuit of the commutator and code matrix unit 31 connected to the selector switch 36 for developing the rhythm pulse patterns to the various tone generators in the unit 41. The motor 32 drives a double-ended rotor 61 which revolves with respect to the rings of the commutator. The outer ring 63 is divided into twenty-four equiangular sub-divisions with an active segment located and isolated from the remainder of the ring at angular locations 2, 3, 4, 5 &c. Certain angular positions do not have active segments, such as positions 1, 13 and 19, since pulses at these particular times are not required for any of the rhythm patterns but at certain intermediate positions designated 1¢, 4¢, 7¢ &c., separate segments are provided to produce pulses for some of the more complicated rhythms. Each of the segments 2, 3, 4, 4¢, 5 &c., at the ring 63 is connected respectively to a horizontal lead in matrix 64, and for simplicity only a limited number of connections are shown necessary to demonstrate two rhythm patterns. Any combination of the basic rhythm pulses can be obtained on output leads such as 68, 69, 70 by connection to appropriate horizontal leads 65, 66 and 67 and to avoid interference between multiple connections to the same horizontal leads, neon tubes 72 are employed, the supply voltage to the segments 1- 24 of the commutator ring 63 being made greater than the striking voltage for one neon tube but less than three in series. The pulse rhythm sequences on the vertical output leads of the matrix 64 are further combined in the selector switch 36 (Fig. 2) to provide combinations of tone impulses. A fox trot rhythm sequence and a waltz rhythm sequence are described in the Specification using two positions of the switch 36. The voltage supplied to the outer ring 63 of the commutator is obtained from a third ring 72 which is a continuous slip ring contacted by a brush 73 carried at one end of the rotor 61 and electrically connected to a similar brush 74. A lead 75 connects a positive 150-volt supply to the slip ring 72. Speed control signals (bi-directional voltage) on line 84 from continuous slip ring 83 are derived from a ring 76 which has pairs of segments 77 and 78 which are negatively and positively charged and are angularly disposed on opposite sides of index points represented by segments on ring 63 numbered 6, 12, 18 and 24. The unconnected small segments 85 between the segments 77 and 78 are the neutral points at which the rhythm follow-up system is in synchronism with the beat supplied to the principal instrument by the player and at these points no voltage is applied to the output lead 84. The tone generators (Figs. 4a and 4b, not shown) comprise eight inputs which are connected to leads 91- 98 of Fig. 2 to supply the input pulse sequence for the individual tone generators. The leading edges of the voltage pulses applied to the tone generators are first rounded and then passed to parallel resonant circuits which simulate the sound of the instrument intended when reproduced through the organ voicing assembly. The motor control circuit (Fig. 5, not shown) comprises a relay contact 135 which is operated in synchronism with the beat on the pedal keyboard of the principal instrument and is such that if the player's tempo is the same as the tempo of the automatic rhythm section, the relay contact closes when wiper 81 is on an unenergized commutator segment 85 between the contact segments 77 and 78. There is then no potential on terminal 144 (Fig. 5, not shown) which is directly connected to lead 84 (Fig. 2) and the tempo of the automatic rhythm section remains unchanged. If the player's tempo begins to speed up, contact 135 closes when wiper 81 is on contact 77 and thus there is a negative potential on terminal 144 which causes the motor speed and thus the automatic rhythm section tempo to increase. Similarly if the player's tempo slows down there is a positive potential on terminal 144, since wiper 81 is on contact 78 when contact 135 closes, which causes the automatic rhythm section tempo to decrease. The speed of the commutator rotor 61 can be manually controlled by means of potentiometer 149 and switch 140 (Fig. 5, not shown). In a further embodiment (Fig. 6, not shown) the relay contact 135 is operated automatically by a characteristic comprising the peaks of the signal from the musical composition played on the principal instrument and which is repetitive at the principal beat of the composition rendered.