I agree with Uncle Dave's posts more than I thought I could ever possibly agree with anyone!

In my duo I work almost entirely with midi-files.

I don't feel bad about that, because they are either programmed by me (either in total or in part), or I have scoured all the internet - (general sites, or exclusive midi-forums) and METICULOUSLY tweaked them, part by part, effect by effect, note by note if need be, to sound EXACTLY like the popular recorded version.
I then wipe all keyboard parts I can play myself, and then play and sing the hell out of the song. As UD says, we have to also continuously scan the ever changing mood of the crowd and keep them on the floor with such a diverse range of genres it's ridiculous.

And crack gags whenever we can!

Sometimes I grab a tambourine or other light percussion (I'm a formally trained drummer as well) and go to town with a great rhythm and lead vocal "frontman performance".

My wife either sings harmony, plays electric guitar (with a cosm amp - changing sounds as style dictates) or then takes over lead vocals (she's a MUCH better singer than me).

We do this almost entirely to Midi backing like I said (occasionally I use the arranger for Old Time Dancing).

We are continually in demand.
We are professionals (no day jobs).
We don't feel like cheats.

Uncle Dave rock on!