Live Coding?

Live Coding is a performance practice where code is written and manipulated live on stage to generate sound and/or video. Following the standards set by TOPLAP, all code manipulation should be projected for the audience’s pleasure. Live coding is situated at the intersection of software culture and art: it enables new and deeper modes of improvisation with computers by exposing and manipulating the innards of software.

More information can be found on Wikipedia. You can find video examples and in-depth coverage of live coding in all its forms on the TOPLAP website.