“On-the-fly programming is a style of programming in which the programmer/performer/composer augments and modifies the program while it is running, without stopping or restarting, in order to assert expressive, programmable control for performance, composition, and experimentation at run-time.”
ChucK is run from a terminal window. The program interprets incoming commands, written in a ChucK-specific syntax, and produces appropriate responses in realtime.
ChucK allows for “live coding” in performance. ChucK and SuperCollider are the most popular programs for this style of computer music generation.