ChucK

Ge Wang and Perry Cook built ChucK at Princeton in 2003. It calls itself strongly-timed: rather than callbacks and timers, you write 500::ms => now; and the program waits exactly that much audio time. The same => arrow, the "ChucK operator", wires unit generators together, as in SinOsc s => dac;.

Code can be added and swapped while the music keeps playing, which made it a natural fit for live coding and for the Princeton Laptop Orchestra, founded in 2005, where each performer played a laptop with its own speaker. Wang went on to co-found Smule, whose Ocarina app turned the iPhone's microphone into a flute.