How would you count this in?

[rpjazzguitar]

Yes, they’re called reading gigs. Pit musicians do this regularly and horn players do it all the time on wedding and corporate gigs booked by talent agencies.

You don’t get to keep the book. Arrangements can cost $75+ for a single song. The bandleader keeps the books.

I forgot to mention about getting calls to sub. Typically, there's a book. In some cases it's something like the RB, meaning mostly one page lead sheets of songs you're likely to know.

But not always. I've subbed in bands reading fairly elaborate arrangements of tunes I didn't know (usually, I get access to the charts on line a few days in advance).

I've also subbed in a group where I expected standards but, in fact, the band book was lead sheets of a lot of obscure tunes (well, obscure to me, and I've played my share of different tunes over decades). Not difficult charts, but completely new to me.

Perhaps oddly, I can't recall ever having been confused by a count-in in those situations.