Shifter is an efficient and flexible software-based, real-time pitch shifter. It goes well beyond an octave shift with no strong timbre artifact (such as the Mickey-mouse effect.) It applies particularly well to the singing voice, or to instruments such as the violin. The applications include the Paganini's Caprice No. 24 transcription (variations 3 and 6) performed by Joshua Bell.

Voice pitch shifted in real time by playing the new pitch on a MIDI keyboard
Because (from the Beatles) slightly out of tune, playing chords on a keyboard
Stradivarius violin pitch shifted to different octaves in real time (performer: Joshua Bell)