STAFF PICK: When Dolly Parton covered Led Zeppelin's "Stairway to Heaven," we had to laugh because it reminded us of the strange marriage of musical genres here. By day (and most nights), this place is a hangout for students in the South UA neighborhood: Pool cues clatter, patrons drink and chatter, an open laptop threatens to tumble off an over-stuffed couch. The music is definitely reflective of the generation. But on two Thursday nights each month from September to May, the Tucson Songwriter Showcase Concert Series moves in. Forty-somethings vie for those same couches to listen to (predominantly) local musicians--amplified but "unplugged." Last year we caught the Betty Diamond band and Tucson's Troubadour and Demaris. The entertainment really begins when a young regular stops short at the entry and has that "I've entered the twilight zone" look. Especially when one of the Thursday regulars is up and dancing to a jig.