Sometimes the creative itch has to be scratched. If you’re Neil Young hooking up with Crosby, Stills and Nash, Buffalo Springfield, or maybe just jamming with Crazy Horse, you might also feel the need for a little time alone. Understandable, actually, trying to juggle so many musical characters.

Likewise, if you’re a Spice Girl, you might not be able to shake the urge to work with Dane Bowers.

Because for all serious musicians (and Posh Spice), sometimes one music project isn’t enough. This month celebrates some of the artists who’ve had too much creative juice for one collective, who need to satisfy multiple muses, or who just have a bunch of extra material that the rest of the band wouldn’t let them squeeze onto the album (not even the special edition, not even b-sides) but knew it was what the world was waiting for. Conventionally, it’s the lead singer who needs to stretch; rarely, it turns out, bass players, although that’s not a universal rule: Duran Duran were hyper-creative enough to simultaneously divide almost the whole group into two side-projects in The Power Station and Arcadia.