Black Francis from the Pixies is widely acknowledged as one of the best singers in rock music, partly because he's willing to sound totally unhinged.
This is what he sounds like without a band backing him up.
If you do this trick with the Pixies song "Hey," he sounds crazy AND kinda perverted and creepy.
Of course, the gold standard for rock stars sounding totally insane in an a cappella track is David Lee Roth's performance on the Van Halen song "Runnin' with the Devil."
Eddie Vedder sounds like a gibbering madman at the climax of the isolated vocal version of Pearl Jam's "Jeremy."
You're probably better off not clicking play on the isolated vocal track for Papa Roach's "Last Resort."
Or this Limp Bizkit a cappella.
Or this one from The Offspring, which sounds like some kind of weird locker room ritual.
Can you imagine just stumbling upon a guy in public making sounds exactly like this? You'd back away slowly.
The vocals for The Darkness' "I Believe In A Thing Called Love" are totally impressive in context, but sound completely silly without any music.
Funny enough, though – Weezer actually sounds kinda cool this way.
Seriously, if you forgive the long pauses, "Say It Ain't So" totally holds up like this.
And somehow, some way, "Love Shack" by The B-52's may actually be more fun with only vocals and hand claps.