I wasn't quite sure how to title this thread.
Very few,if any steel players are gigging every week,most of the guys I know can go for weeks without a gig, so depping or playing with a band other than Your "own" band is common.
If another band asks YOU to play with them do You accept the gig and keep Your word or do You make it clear that if Your regular band get a job on the same date You will have to cancel
The problem has never arisen with Me but I would honour the first entry in My diary.

