In music, many different notes form a chord which together forms a key. There are instruments that are ‘electronically’ keyed. When played together in proper sequence, that ‘key’ unlocks the door to that instrument’s particular circuit, and that instrument only! No other instrument has that same key or is tuned to respond to that same key. And only when that sequence of tones — that key of its music, is played to that particular instrument — only then does that…..