Two years after Smash Mouth scored its biggest hit with a remake of "I'm a Believer," the band still sounds like a modern-day Monkees. On the California quartet's fourth CD, they continue to deliver relentlessly sunny, instantly catchy pop ditties that you can imagine Davy Jones and company playing in the '60s. In fact the ska-pop single "You Are My Number One" is a previously unearthed gem by Neil Diamond, who also wrote "I'm a Believer" for the Monkees. On other tracks Beach Boys-style harmonies and swirly, psychedelic-tinged keyboards add to the retro charm. Smash Mouth keeps its lyrics as lightweight as its music, even on the post-Sept. 11 party song "Hang On": "If things are getting rough/ Turn it back around/ You gotta turn it up when they tell you tone it down," sings frontman Steve Harwell in his bar-band voice. And there is a sameness to some of the tracks that shows the group's musical limitations. At least, though, Smash Mouth knows not to bite off more than it can chew.