"P.A.R.T.Y.," the new album from Dog Party, a.k.a. sisters Lucy Giles, 13, and Gwendolyn Giles, 15, does not entirely put away childish things.

Dog Party's first full-length album includes a song about the girls' rabbit friend, Chihiro. But the "Rock 'n' Roll High School" insistence of the title track, combined with rootsier material and richer overall sound, speak to the places the sisters have been since they began playing together at ages 9 and 11.

Like the stage at the summer Concerts in the Park series, and Luigi's Fun Garden, where Dog Party returns tonight for a vinyl release party for "P.A.R.T.Y." with Nacho Business and Kepi Ghoulie.

Or the truck stops in Arizona and New Mexico, where Dog Party toured over the summer with Ghoulie and fellow Sacramento band Pets.

"We learned the do's and dont's" of the road, guitarist-singer and high school sophomore Gwendolyn said last week at her family's Carmichael home.

Variety is key, the girls learned, to meals sourced from shelves of gas station mini-markets. There's also a science to the quick loading and unloading of equipment.

"You have to be very, very organized," said drummer-singer Lucy.

Lucy and Gwendolyn are now the same height, and both sport braces. The pink streak in eighth-grader Lucy's hair goes well with her Kepi Ghoulie T-shirt.

Their musical equipment's permanent home is in the family's living room, where Dog Party put on an impromptu concert amid the White Stripes and Ramones posters. Their playing was fast and structured, their voices not quite as high as when they recorded "P.A.R.T.Y."

"We were chipmunks" in earlier days, Gwendolyn said with a grin.

They performed some songs from "P.A.R.T.Y.," others from their self-titled 2009 EP and new ones. The set reflected Lucy's current fascination with the Ramones, Gwendolyn's developing melodic instincts and the sisters' shared musical ingenuity. Dog Party can go acoustic or semi-acoustic, which is what they call it when Gwendolyn turns down her buzzy guitar and Lucy plays acoustic guitar and, simultaneously, bass drum and high-hat with her feet.

They perform like seasoned musicians at home, just like they do at Sacramento coffeehouses and all-ages venues. The nerves start, said their dad, Sam Giles, when they perform with veteran musicians like Ghoulie, who recently brought Lucy and Gwendolyn on stage during a San Francisco show.

"When they are playing with more- established musicians, they want to raise their game," Sam Giles said.

At tonight's vinyl-release show, Dog Party will play as a duo and then as part of Ghoulie's band. Ghoulie came to the Giles home last week to rehearse.

"I like melody, and they have great songs and a great stage presence," he said.

Like countless rock musicians before them, the Giles sisters resist attempts to group their music thematically. "P.A.R.T.Y." consists of unrelated songs written at different times, they said. But they acknowledge a more general, punk-rock-appropriate thread connecting much of their repertoire.

A lot of songs are about being mad at people, they said.

Even if the emotion is fleeting, the sentiment "adds to the vocals," Gwendolyn said.

"And you have to mean it," Lucy added with a smile, "and then you hit the drums really hard."

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