I honestly don't know if DB was acting the bad singer or if he actually is a bad singer. His version of "Mandy" was so grating to me, I couldn't even laugh.
Whichever it is, I'm still guessing we should just be glad that the musical was done on Buffy and not on Angel, lol! That said, I recognize that just about every main character on Angel did get to sing for Lorne at one point or another - even if it may have just been a line or two, and I think Charisma Carpenter sang for us way back in Season 1 of Buffy in "Puppet Show" before anyone else did. Julie Benz aka Darla has a beautiful voice.