There's a time and a place for everything. Imagine a live version of the Cornelius Brothers And Sister Rose hit "Too Late To Turn Back Now" without strings. You either have to be creative and do a reggae version of the song, get a decent keyboard player to do it right, or sound like a moron for attempting a live version of a song you know you're only going to butcher thereby ruining everyone's night out. That's the right place for a backing track. Being too lazy to learn the set list isn't the place.