Meh. This sounds like an exercise in trying to make someone look bad/embarass in a live situation (kinda like the house band switching the key up on a musician in an open jam so they sound out of key). Like others mentioned, not my kind of gig...but also I dont play covers. I'd be fine and make decent music but I would miss the changes and certainly not play any lines that are true to the actual song unless by sheer luck I choose the same notes or general groove as the actual song.
To me, playing covers is not the measure of being a musician...its the measure of woodshedding on lots of cover songs. The measure of a real musician is someone who can play and have a musical conversation by just listening and responding.
For me...
Its a show up and play job for a crowded bar you have only talked to the drummer online. He has a guitar player friend who is supposedly really good coming and he is bringing a trombone player. There is also a keyboardist that the drummer just met but has never played together. No one is pro, but everyone has the chops and abilities of pro players...they just all have families and day gigs. Nothing planned, no set list, no discussion...fully improv, use your ears, listen for the tonic center. 2 60 - 90 minute sets
How do you feel about that?
This is the gig I LOVE and look for. IMO, this is what being a musician means. Its the difference between knowing how to play an instrument vs knowing how to play some songs.
Ok, so I'm going to make some enemies here. The pros I know (myself included) would not take that gig if it was the last gig on earth. A jam, sure. I love that. That's for me and for them, NOT for the audience, unless they're going to a jam night and they know what they're getting. A paying audience deserves the respect of at least having sat down and run a couple of numbers. The gig you describe is all about ego. Put your ego back in the case, and prepare for an audience. Again, just me, personal opinion.