Key assigner

A key assigner comprising:

• key state memory means for storing signals representing previous states of depression and release of respective keys by each key;
• a keyboard circuit for simultaneously and parallelly delivering signals corresponding to the ON-OFF states of key switches interlocked with the respective keys;
• change detection means comprising a logical circuit for comparing by each key the signals provided from said key state memory means with the signals provided from said keyboard circuit and detecting change from the previous state of the key switches to the present state thereof at a predetermined time interval;
• a priority circuit for selectively delivering out a single signal from among change detection signals supplied from said change detection means in accordance with a predetermined priority order at said predetermined time interval;
• a key code generator for generating key codes corresponding to the change detection signals provided from said priority circuit;
• a key code memory having channels equal in number to a maximum number of tones to be reproduced simultaneously and being capable of storing the key codes in the respective channels;
• key state detection means for detecting whether the key code supplied from said key code generator corresponds to a newly depressed key or a released key;
• key code loading means for loading the key code from said key code generator in a corresponding channel of said keycode memory if the key code corresponds to a newly depressed key;
• a decoder for decoding the key codes provided from said key code memory;
• and
• control means for causing said key state memory means to store signals representing states of depression and release of the respective keys in accordance with the decoded signals provided from said decoder;
• tone generation control signals being produced on output lines of said decoder corresponding to the respective keys.