What do you get when you cross the Saturday Night Fever soundtrack with the Grateful Dead? Disco jam band Poolside shines their liquid light shows on spinning mirror balls, creating a syncopated psychedelic sound that would inspire just about anyone get up and start Napoleon Dynamiting across the dance floor. The group formed around San Francisco DJ Jeffrey Paradise and Junior Senior bassist Filip Nikolic, who launched Poolside out of L.A. with their 2011 single “Do You Believe.” That song’s sparsely arranged electronic sound was fleshed out somewhat on their debut album, but last year’s sophomore release, Heat, was more of a full band effort, featuring additional players, banks of space age electronics, and a new focus on guitar interplay clearly aimed at filling concert sets with improvisational Phishing and Spin Doctoring. Their December 27 show at the Music Box is likely to be highlighted by recent tracks such as “Everything Goes,” which they debuted a few weeks ago at San Francisco’s Outside Lands festival. The band’s touring incarnation includes two members from goth rockers the Rapture, Vito Roccoforte and Mattie Safer, as well as Casey Butler (Pharaohs) and Brijean Murphy (Toro Moi).