Asynchronous tone generator

DETAILED DESCRIPTION In its most general form, as seen in FIG.
1, an electronic musical instrument, for example an electronic organ, has a keyboard 10 or other form of player-operated means for selecting the notes to be played.
The output of the keyboard is transmitted over a cable 12 to the priority note assignment control logic 14, which assigns the task of production of the required tone signal for each note to a selected one of a plurality of frequency dividers 16.
Each divider 16 receives a clock signal of high frequency f from a common source 18, and divides it down by the appropriate division ratio to produce the required musical tone output on one of the lines 20.
This is a time shared system, in which there need not be as many frequency dividers 16 as there are individual musical notes within the range of the instrument.
On the contrary, the number of frequency dividers 16 may be much lower than the number of notes, because each frequency divider is capable of varying its divisor so as to produce any one of a plurality of different notes on command.
The necessary divider selection command issues from the priority note assignment control logic 14 over the appropriate one of several control cables 22.
How the logic 14 makes a specific choice among the frequency dividers 16 depends upon the specific system architecture, as explained below.
But in any case, the command signal which is issued by logic 14 over one of the cables 22 to the selected frequency divider 16 includes information, derived from one or more read-only memories (ROM's) 24 included in the logic circuitry 14, as to which particular divisor value (let's call it D) must be employed at a particular time by the selected frequency divider 16 in order to produce the selected musical note.
Thus, the logic circuitry 14, in general terms, receives a command that a selected note be played, selects one of the frequency dividers 16 to divide down the clock frequency f to produce that note, "looks up" the proper divisor for accomplishing that task in the information stored in a ROM 24, and causes the divisor information obtained from the ROM 24 to be transmitted to the selected frequency divider 16