Hailing from St. Louis, rock quartet Cavo plays no-nonsense, American-heartland style rock with a clean, driving edge. On Bright Nights * Dark Days, Casey Walker’s lead vocals bring to mind the likes of Lou Gramm, Paul Rodgers and similar straight-ahead rockers of a generation ago. But a touch of grunge angst and nü-metal austerity saves Cavo from retro status. The playing here is sharp and tight, with Brian Smith’s punchy bass lines deserving special kudos. “Champagne,” “Cry Wolf” and “Blame” draw upon the group’s tougher side, while “Beautiful” and “Useless” are moodily introspective. If Cavo comes on strong instrumentally, their melodies can be disconcertingly sweet and “Ghost,” co-written with the Nixons' Zac Maloy, has the lilt of a country-pop radio hit. Lyrically, the band is most comfortable winking at romantic intrigue (“My Little Secret”) or yearning for inner change (“Let It Go,” “Useless”), and ultimately, the melodies and lyric themes here matter less than the crunch and thump of the music.