I have yet to try riding to jam sessions carrying my guitar and pedals on a bike, abit unsafe i guess. Especially when im riding a sportsbike.
Theres a few possibilities though, ask your pillion to hold it for you, or like goose suggest, vespa is the way to go. I've seen uncles carrying those tall fans on it also. Hahahaha.
Other then that, i suggest you go public or drive. Be safe then sorry. XD