Improvements made to a computer controlled digital music synthesizer are described. The basic elements of the synthesizer are discussed to give the background for these developments. Hardware additions have been made to extend the technical capabilities of the system and provide the user with computer control over various aspects of a musical sound including tremolo (frequency, amplitude and waveshape), the attack and decay rates of the notes and the volumes of the notes. Emphasis, however, is placed on describing the software developments, which are designed to provide the user with powerful facilities which are easy to use even if the operator has no computer training (as is likely with musicians). The software allows the user to interact with the timbres being produced by the synthesizer and to develop complete performances which can then be played by a computer. All aspects of the synthesizer are controlled by the computer.