Before the current crop of boy bands started insisting they were vocal groups, not teeny bop darlings, All-4-One was actually making a name for itself as a vocal group -- first with "So Much in Love," their '90s take on doo-wop hit, then with the record-breaking superballad "I Swear." The group's debut included a few funk-driven numbers, but the midtempos on their fourth album are more sweet than sexy ("No Doubt," "If You Want Me"), with the exceptions of the low-down groove "Secrets" and the disco dance-floor jam "Keep It Goin' On." The '70s isn't the only era the singers throw back to either. "One Summer Night" recalls the doo-wop stylings of the '50s, and many of the love songs have a vintage pop-soul feel. Masters of harmony, All-4-One do best when keeping it simple (the quiet "I Will Be Right Here") and steering clear of cheesy lyrics (as they fail to do on "Smile like Mona Lisa"). ON AND ON is the document of four young singers exploring different avenues for their maturing sound -- and these voices will carry All-4-One much farther than the latest pinups.