Each of the actors (Jaleel, Kenan, Dulé, and James) did his own singing.

DalekSec you're right I watched it again and payed closer attention to it this time. I was thinking now here's a made up group with a really good sound, even with Shawn joining in. I knew Shawn and Gus could sing from American Duos and I think they could build a show around Quarter Black being on a show like America's Got Talent and having to solve an unrelated case at the same time. I'd like to hear more of them doing Gospel music if they don't show Shawn moving his mouth weird while he's singing.
I was disappointed in the way Jules treated Shawn and Gus like they were untrustworthy after all the cases they solved. I do wonder now who would win in a fight between Guss and Lassiter. You'd think that after being shown he's not as good a detective as Shawn he'd get over it. After all Shawn is the one who proved Lassiter wasn't guilty of murder in "Lassie Did a Bad Bad Thing", and in the processsaved his life by grabbing Detective Drimmer's gun and Shawn kept the chief from finding out Lassiter's car was stolen from the Police Station parking lot in "Zero To Murder in Sixty Seconds."

I'd argue that Lassie saved Shawn's life in that episode. It's a two-way street. But I see your point.

I would go so far as to say in this case it was close to a toss up but Lassiter would never had time pull the pistol out of the bowl had Shawn not first grabbed Drimmer's.
I forgot to say that when I watched "High Top Fade Out" the second time I saw that the Theme Song was sung by Boyz II Men I think the Quarter Blacks could have done it.