Great Backing track app
I use this to send a click, and a cue track, all separate from the backing tracks. Some singers (like mine), don't love the click too loud, so I can turn it down just for them, while still leaving the cues loud. Also, the multitracks are configurable, so if, for example, my keyboard player can't make a gig, I could choose to turn on the keys track just for that gig.
I only have one suggestion to improve: it would be great if ST3 could play a midi file along with the audio. Currently we can use midi output to control lights, other equipment preset changes, etc. but this has to be programmed in manually. Would be awsome if we could just drop in a midi file with the appropriate CC/PC messages.