We're a 5-piece 80's cover band (bass, drums, guitar, keyboards, female singer). Our keyboard player wants to be able to sub any member that's needed for a gig that they can't make it. I feel only myself (bass) and the drummer are "sub-able." What are your opinions on who can and can't (or shouldn't be) subbed for? Is there any member of the band that is completely off limits to subbing? Thanks!