Email is for pussies. Don't be a pussy.
Tell them you're looking to do other things. Promise to cover the dates you have booked (within reason) so they can find a replacement(s) and move on. Be prepared to be moved on early if they decide they found someone who's ready.
Do this in person.
this is the best idea, IMOWrite a song about leaving the band, have them all learn it.
I'm hearing the "Real Men of Genius" song playing in my head.Write a song about leaving the band, have them all learn it.

I suck at confrontation, so the email thing appeals to me. I hope to remain friends with the singer, but the other 2 guys I really don't care as much about.
Well, there are pros and cons here. If I wait to tell them at the next band meeting, I'm kind of a dick, when I could email them and give them an additional 6 days to find someone, and I would have another 6 days to put an ad out on craigslist. However, if I do it by email, I'm a dick who can't do this stuff in person. So either way I'm a dick.
No, I've held off on booking anything knowing we might be exiting.Do you have any upcoming gigs?
No, I've held off on booking anything knowing we might be exiting.
If there's no impending gig, then a 6-day delay is pretty negligible in the grand scheme of things. You've already been mulling this over for some time, I take it.Well, there are pros and cons here. If I wait to tell them at the next band meeting, I'm kind of a dick, when I could email them and give them an additional 6 days to find someone, and I would have another 6 days to put an ad out on craigslist. However, if I do it by email, I'm a dick who can't do this stuff in person. So either way I'm a dick.