Key code data generator

In combination with an electronic musical instrument having a note selection keyboard and switches for the selection of performance functions, a key code data generator comprising:

• a note detection circuit operatively connected to said keyboard and to said switches and having a set of storage cells, individual storage cells being assigned both to a respective note name in a musical octave and to a specified performance function, and an encoder directly connected to said set of storage cells for providing note codes identifying the cells containing data,
• a chord detection register having a separate stage corresponding to each note name, and associated chord detection logic for detecting chord types by the relative position of data in said stages, and
• control signal formation means for providing sequential first, second and third sets of control signals which operate said note detection circuit sequentially in:
• a first mode in which said first set of control signals causes data indicative of selected function switches to be entered into ones of said storage cells assigned to the corresponding functions, said encoder then providing note codes representing said selected performance functions,
• a second mode in which said second set of control signals causes data representing keys selected on said keyboard to be entered into storage cells assigned to note names corresponding to the selected keys, said encoder then providing note codes representing selected notes, said selected key representing data also being entered into corresponding stages in said chord detection register in the event that, during said first mode, the note code for a certain selected performance function was provided, and
• a third mode, enabled by provision during said first mode of said note code for a certain selected function, wherein said third set of control signals causes said chord detection register to be recirculatingly shifted in synchronism with successive provision by said encoder of note codes for each of said storage cells, detection of a chord by said detection logic causing said control signal formation means to generate a signal which gates the note code concurrently provided by said encoder to a key code register, said gated note code identifying the root note of said chord.

On a single integrated circuit chip intended for use in an electronic musical instrument of the type having note selection keys and performance function selection switches, said keys and said switches being arranged in blocks connected to said chip by common block lines:

• first circuit means for scanning each block of performance function switches to detect operated switches and to produce corresponding performance function designating codes for control of circuitry on said chip, and
• first output means for externally delivering said performance designation codes only to said instrument via an output terminal on said chip,
• chord detection circuitry on said chip,
• a second circuit means for scanning each block of keys to detect depressed keys and, in response to production by said first circuit means of certain codes designating specific automatic performance functions, to supply data representing detected depressed keys to said chord detection circuitry
• a second output means for supplying to said instrument, via a separate output port on said chip, multibit note codes representing detected depressed keys detected by said second circuit means, and
• third circuit means, enabled by production by said first circuit means of said certain automatic performance function designating codes and including said chord detection circuitry, for detecting the chord type and root note represented by said depressed keys, and for supplying via said output port note codes, based on the detected chord type and root note, for an automatic performance of the type designated by said certain function designating codes.