Frank:

Here's one candidate:

http://www.motu.com/products/software/dp/

and there are many others. Ableton Live has a good rep although I find it somewhat arcane to use. Hell, Apple's own Garage Band lets you sequence tracks and is user-friendly.

See http://www.mp3machine.com/mac/RECORDING/ for some choices.

Here's an even fuller list: http://www.hitsquad.com/smm/mac/.

Studio Vision Pro may fill the bill for you.

Regards,

Amos