both!
Its a 2 man show, and they do some singing, but only as part of the show! Just trust me on this one, these guys are amazing.
I saw their first show at the Catalina about a year ago, and went back the next night for more!
They do the whole thing themselves, from the writing, to the set, to the acting.
Simply amazing!
(check out fridays paper - the tonight section - for a good review)