It happened to me on 'New years Eve' a guy at the end came up and introduced himself as a keyboardist, he'd been listening to me all night performing on my PSR3000 topped with an additional synth keyboard. I'm backing 2 vocalist's and adding backing vocals and playing in excess of 50+ numbers in original keys trying to add parts on top of the arranger to emulate the songs we played close to the original orchestrations , the guy asked where I got the arrangements from?
No arrangements 'mate' I said, I manipulate drum, bass and additional instruments loops via chording to match the song chords progressions of the originals, if I walk away form the keyboard so do the arrangements!...HE walked away looking very confused...but it was good to think that he thought he was listening to pre-recorded arrangements, he obvioulsy did'nt hear my mistakes!

Rgds
Noel J