GB1391617A - Automatic chord playing apparatus - Google Patents

Abstract

1391617 Electrophonic musical instruments WURLITZER CO 23 May 1972 [17 June 1971] 24252/72 Heading G5J An electrophonic organ comprises a plurality of keys and pedals with corresponding tone generators, a plurality of electronic gating means connected to the tone generators, means for producing two sets of pulses and directing one set to pass pedal tones through first gating means and the other set to pass musically related chords through second gating means and means interconnecting the pedals and the second gating means to render the latter conductive independently of the pulses. A system of a clock 10a, Fig. 2, and logic circuits 12a, 14a generates strings of pulses which, after shaping to the desired form, open diode gates to produce percussion, bass notes and chords in a rythm selected by manual switches. Each gating pulse is shaped by a monostable (120 or 152, Fig. 3, not shown), a diode (126 or 162) and a capacitor (128 or 164) to have a fast rise, a short plateau, and an exponential decay, to give the desired attack and decay characteristics to the sounds. In the preferred embodiment LC master oscillators 64 and dividers 66 produce four octaves of square wave tones which, with suitable filtering, are used for the keyboard and pedals, for the automatic bass notes and chords, and for some of the percussion sounds. Other percussion sounds are obtained from a white noise source. For the bass notes, one of seven tones from the dividers 66 is selected by a push-button switch 300, Fig. 4, and fed, via a divider 54a (86, Fig. 3, not shown) which halves the frequency, a diode gate (90) and an amplifier (94) to an output line 26a (96). For the chords, gating pulses are fed through one of twenty-one push-button switches such as 258, corresponding to minor, major and major seventh chords for the seven bass notes, to a diode matrix, part of which is shown at 256. The matrix routes the pulses to appropriate diode gates (shown in the centre of Fig. 4) to open the gates to pass appropriate tones from the points 236 (fed from the dividers 66) to a line 98, from which the tones pass through an amplifier (100, Fig. 3, not shown) to the output line 26a (96). There are five lines (Fig. 3, not shown) carrying pulses to the pulse-shaping circuits. Pulses on the "bass drum" line (116) produce bass notes. Pulses on any or all of the lines, according to the settings of rhythm switches, produce chords. The pulse-forming circuits can be disabled, if desired, so that chords and bass notes are sounded whenever the push-buttons are operated. In a simplified embodiment (Fig. 1, not shown) the pedals and keyboard are omitted and LC oscillators generate tones for the chords directly, only one divider (54) being retained for the bass notes. Also described is an arrangement (Fig. 5, not shown) in which only manual operation is possible, the pulse-forming circuits being omitted.