[MATH POP] Tender, the four-song sophomore release from Portland trio Wax Fingers, finds the group growing further accustomed to life within its oddly colored shell.

A group of psychedelic day trippers with a physics professor's love of intricacy, Wax Fingers has built its reputation by plying math-rock minutiae with the colorful melodic pull of pop. The group's self-titled debut overindulged at times in self-seriousness, but Tender suggests that Wax Fingers's approaching maturity will be marked by the joyful imposition of form onto the band's collection of sonic bric-a-brac.

Armed with guitars, synthesizers, omnichords and a variegated percussive tool kit, Wax Fingers likes to pile its trickling riffs atop one another until they assume the tidal force of a song. Tracks like "I'm So Limber" and "Almost Always Sailing" (Tender's dual highlights) don't begin so much as emerge.

Pete Bosack provides vocals for these experiments, but the human voice, for the most part, serves as simply one more of Wax Fingers's tonal toys.

If this is starting to sound like a description of pioneering pop-leftists Battles, that's because, well, Wax Fingers sounds an awful lot like Battles. Even the cover art for Tender recalls Battles' recent fetish for creepy renderings of food.

However, Wax Fingers distinguishes itself from its progenitors by dint of its comfort with pop forms. Tender balances the prodigy's need for a challenge with the pop artist's structural conservatism. In the end, Wax Fingers' strategy furnishes improvements to both.

SEE IT: Wax Fingers plays Rontoms, 600 E Burnside St., on Thursday, Aug. 23, with Aan, Palma Dana Buoy and Parenthetical Girls. 7 pm. $10. 21+.