This is very cool. An article in Wired features a member of london.pm

Some DJs spin vinyl or twiddle fader knobs. Others write subroutines in C++.

A new brand of music maestro is turning programming into performance, eschewing turntables for a compiler and a mind for syntax structure. “Livecoding” practitioners improvise using Perl or homemade programming architectures to build compositions from the ground up, replacing instruments and samples with raw code authoring before a live audience.

Alex Maclean, a U.K. livecoder and art student, said he traded in his guitar when he found he could be more creative with code than with strings. He touch-types using Perl at raves and dance clubs, creating a unique visual and musical experience. Sessions with drummers, MCs and other livecoders can be reminiscent of traditional free-jazz improvisation.