Chord recognition system for an electronic musical instrument

Abstract

A chord recognition system for an electronic musical instrument, namely an electronic organ. A shift register receives data information from the keying lines of selected playing keys. The pattern of the received data is compared against selected normalized chord patterns in a program logic array to determine if the note input sequence is in a known musical relationship such as major, minor, minor sixth, seventh or others. A chord logic circuit receives the information from the programmed logic circuit and further reduces the information to output signals indicating a major, minor, or seventh chord and a pattern found signal. If no chord pattern is detected in the input data sequence, the register shifts the data on its first input line to its last input line and all other data is transferred downward accordingly. A counter sequences at each shift of the data input information. The shifted data is now compared in the programmed logic array as described above. This operation is repeated until a pattern match is found or an entire shift cycle is complete. The type of chord being played is indicated by the output of the chord logic circuit and the root or alphabetic key of the chord being played is indicated by the output of the counter. Each step of the counter indicates a different root or tonic note. Thus, the system recognizes normalized chord patterns and tracks the alphabetic key for recognizable chord patterns. The output from the chord logic circuit and the counter are used as inputs to other organ circuits such as a visual display circuit to illustrate to the organist the chord being played.