Don't forget the amplifier, they have waterproof stowage in the hanger on targets, Boats of cours have the music room so no problems there. There are good reasons for musical types to go the boat route, the music can be appreciated by everyone during the regular silent routine
Jack, despite the question being asked before which a simple search would have found as Tommo has shown, it's not a daft question as you are right that space is limted. I would suggest that you don't pitch up on day one with it but first have a word with your mess killick to find out if and where you can keep it before bringing it onboard.
For others wishing to bring different types of musical instruments onboard, I know of people who have been able to bring on a full drum kit but as a 'baby matelot' you will unlikely be given permission for something like that. Before anyone asks, don't even think about bringing on a grand piano and a concert harp might be a bit of a struggle.
It is also refreshing to be able to read a question from a newbie who has bothered using comprehensible English as opposed to the usual thick and lazy twunts who seem to think that not bothering to write properly is actually a cool and trendy thing to do.