In regard to music, the parameters of the term “pop” have been stretched and tested and toyed with so thoroughly and for so long that it’s hard to know what, if anything, someone means when he or she describes a song or a band or an album as “pop.” But if we put commercial viability out of our minds for a moment — because pop is a sound, after all, and not a number — there’s a handful of attributes that have always accompanied pop music of all stripes: amalgamating various contemporary and bygone styles, a focus on melody and danceable rhythms. While locals Mom and Dad don’t emphasize pristine performances or the high-tech production commonly associated with pop music, this year’s Cave Art is absolutely pop music. It’s sloppy, fuzzy, lo-fi and couched in aesthetics typically reserved for garage-rock bands — and, technically, Mom and Dad is of course a garage-rock band — but it’s insistent, catchy, upbeat music with undeniable power-pop melodies that could probably be called “happy” if they weren’t so youthfully angst-ridden. Cave Art is pop the same way that … well, cave art was pop. It’s folks expressing themselves viscerally and simply, and with an accessibility that we can all grab onto if we just pay attention. Headlining tonight’s show will be badass up-and-coming local psych rockers Ranch Ghost, and Don Coyote and Bad Back round out the bill.