The Hardware units work in Realtime.

Some of them can take an audio input from say a guitar that you are playing, and analyze that and derive the right vocal harmonies around your voice in the mic input. This is fantastic and works very well.

Some of them also have a MIDI input that can do the same as the above for MIDI keyboardists of the like. As long as the unit can get the chord, it can make the harmony that matches.

Also, the newer technology in these hardware units is rather amazing as to realism of the voices it creates.


--Mac