A programmable tone generator for an electronic musical instrument generates a pulse train output (F out) in which in each cycle the starting time and duration of each pulse is controlled, thereby to determine the harmonic content of the electronic waves that are converted to audio sound. A binary counter (12) serves as a time base for encoding each period of a tone signal waveform into plural outputs (14) in the form of a binary code. A plurality of programmable tone generation circuits (16) are coupled with selected counter outputs (14) to comprise plural tone signal branchs (16), each providing a tone signal at a selected fundamental frequency and having selected harmonic content. Each tone signal branch (16) includes a programmable variable code generator (26) and determines the initial content of the output waveform, subsequently either maintaining or changing the fundamental frequency and harmonic content thereof.