Our long-standing, knee-jerk aversion to undie rap is in peril after hearing this live bedroom performance by a young man who calls himself P.O.S. (quit hatin’ … on yourself, dude). Outfitted in a crisp flannel shirt, Stefon Leron Alexander — his given name; really, what must his mom think of him calling himself piece of shhh? — rips out a startlingly great cover of Pearl Jam’s “Why Go,” off (the newly reissued) Ten. This is something like a cross between “Chocolate Rain” and … shit, we don’t know. But it is awesome.