terminatorX is a realtime audio synthesizer that allows you to "scratch" on digitally sampled audio data (*.wav, *.au, *.mp3, etc.) the way hiphop-DJs scratch on vinyl records. 

It features multiple turntables, realtime effects (built-in as well as LADSPA plugin effects), a sequencer and an easy-to-use gtk+ GUI.

WWW: http://www.terminatorx.org