There are different kinds of ships where you play different kinds of music. There are ships where the bands get like two or three weeks of rehearsals on land and then join the ship. All that these bands do, is to play there sets, and sometimes they backup for guestperformers. The bandmembers usually stay the same during the whole contract.
On other ships you don't get any rehearsal time on land. You join the ship as a musician and join the already working band, which is usually a ten piece band. They play sets, they play all the productionshows (sight reading) and backup the guestperformers. The best part (or maybe worst...) about these bands is that the musicians constantly change. You may have joined the band two weeks ago, and the guitar player already leaves in two weeks and a new one is coming. This way you gain a lot of experience because you play with many musicians but it's also something bad, because you can't really connect to the people. That's something that is really hard on the ship anyway.
We do get a lot of requests. All of the bandmembers got an IPad with all the sheet music on it. That way the guests could just call a song and if we had the charts for it we would play it. There are also guests that bring their instruments, like guitar or sax, and they ask if they could come on stage and jam with us... they're usually really really bad but always a lot of fun.
I hope I could answer your questions.
