Electronic musical instrument with means for automatically generating chords and harmony2010-02-05 00:00:00lines 116 are connected individually to its three stages. The state of the counter 114 is incremented by one for each complete cycle of thecounter 108, so that the signals on the output lines 110 and 116 form a cyclically repeating pattern for every seventy-two clock pulses. Seventy-two clock pulses constitute a single cycle of operation of the multiplexer, during which the status ofseventy-two switches is sensed, to derive information relative to operation of the instrument.
The output lines 110 of the counter 108 are connected to four input lines of a one-of-twelve decoder 118, which functions to decode the binary representation of the signals on the output lines 110 and energize one of twelve output lines 120, inaccordance with the state of the counter 108. The twelve output lines 120 are designated in FIG. 4a as the "X" outputs and are numbered zero through eleven, to indicate the state of the counter 108 when each respective X line is energized.
The X lines 120 are connected to the keyboard switches and the function switches, through diodes 121, as illustrated in FIG. 3. The keyboard 10 is represented schematically, and under each key of the keyboard 10 there is a keyboard switch 124which is actuated when its corresponding key is depressed. Each of the switches 124 is a normally open, single-pole, single-throw switch. One terminal of the switch is connected to one of the X lines 120, and the switches 124 which are associated withcorresponding keys of the keyboard 10 in different octaves are connected to the same X line 120. Thus, the common poles of all of the A keys are connected together, through diodes 121, to one of the X lines 120, the common poles of all of the B-flatkeys 124 are connected in common to a second of the X lines, etc.
The other pole of each of the switches 120 is connected to one of several Y lines 126. The Y lines 126 are connected to the switches 124 in accordance with their octave location relative to the keyboard. Thus, the first of the Y lines 120 isconnected in common to the second terminal of the first twelve switches 124 (for the highest octave), the next Y line is connected in common to the next twelve switches 124, etc. A total of sixty-four keys are provided in the keyboard 10, and there aresixty-four switches 124 connected in the manner partially illustrated in FIG. 3. The last of the Y lines 126 is connected to four switches 124 of the lower left-hand end of the keyboard 10 (not shown), and to eight function control switches 129 through136. The Y line is connected to the second pole of the switches 129 through 136, with the first terminal of the switches 129 through 136 connected to the last eight of the X lines 120.
In operation, one of the X lines is energized with a signal in the manner described above, in accordance with the state of the counter 108. This signal is then applied to all of the switches associated with keys for the same note name and, insome cases, to one of the function control switches 128-136. Each of these switches 124 which is closed completes a path from the energized X line to one of the Y lines 126. The Y line which is energized by any closed switch depends upon the positionof that switch in the keyboard. A switch in the highest octave will energize the first Y line, a switch in the second highest octave will energize the second Y line, etc. If the energized X line is connected to a closed function control switch, the lastof the Y lines is energized. For any given combination of X and Y lines there is one and only one switch which can complete a path, and this one switch may be either a keyboard switch 124 or a function control switch 129-136.
The Y lines 126 are connected to six inputs of a six-channel multiplexer 128 (FIG. 4a). The multiplexer 128 receives its control inputs from the output lines 116 of the counter 114, and functions to connect one and only one of the Y lines 126 toan output 130 of the multiplexer 128, in accordance with the state of the counter 114. The output line 130 thus contains, for each cycle of operation of the multiplexer 32, a train of pulses, including one pulse for each of the operated switches 124 and129-136. The pulses are encoded in time position representative of the switches which are operated. Hereinafter the seventy-two pulse times of each cycle will be referred to as pulse time 1 through pulse time 72. Pulses occurring during the firstsixty-four pulse times represent operated keys of the keyboard, while the last eight pulse times represent operated ones of the function switches.
Note Latches
The identification of the note corresponding to a pulse within the first sixty-four pulse times corresponds to the binary coded output on the lines 110 at the timme of occurrence of such pulse on
the line 130. Similarly, the octave of such note(the octave of the keyboard in which its associated key is located) is identified by the binary code on the output lines 116. Thus, the simultaneous condition of the outputs 110 and 116 uniquely represents the specific switch which is being scanned atany instant. These seven lines, viz., the four lines 110 and the three lines 116, are connected to seven inputs of a group of A latches 132 and to seven inputs of a group of B latches 134. The A latches 132 are provided with a set input 136, and, whenthe set input is energized with a set pulse, the latches 132 are set in accordance with the signals then present on the lines 110 and 116. That is, a high level on one of the lines 110 and 116 at the set pulse time causes its respective latch to be setin one state, and a low level then causes it to be reset to the opposite state. A similar set terminal 138 is provided for the B latches. The set inputs 136 and 138 are energized with set pulses at specific times, as described more fully hereinafter.
Seven output lines 140 connected to the A latches continuously manifest voltage levels representative of the states of the individual latches 132. Similarly, seven output ines 142 manifest the states of the B latches 134. The lines 140 areconnected to seven inputs of a group of C latches 144, which is provided with a set input 136. When the set input 136 is energized, the C latches 144 are set in accordance with the signals on the lines 140. Similarly, the lines 142 are connected toseven inputs of a group of D latches 148, which has a s...
