HOBOKEN, N.J. — John McCauley, gaunt and scraggly, clutched an electric guitar at Maxwell’s here on Monday night, finger-picking a lone song, “Houston, TX,” by himself. His band, Deer Tick, had spent the past hour digging into roadhouse country and rawboned rock ’n’ roll, with a bluntly effective fervor. This solo interlude seemed like an unscheduled detour, announced on the fly. But it was a clear, vital moment in an unfocused show.

“Houston, TX” comes from “Born on Flag Day” (Partisan), Deer Tick’s winningly ragged 2009 album, and in the original arrangement it’s a lilting shuffle, offered in tribute to the