There’s a moment on an old Sonic Youth live recording where, seeing that Thurston Moore is having trouble getting his guitar into its proper, highly unconventional tuning, Lee Ranaldo says, “We promise a new tuning every night, ladies and gentlemen!” It’s a throwaway line, but there’s poetry to it: Where else, in 1987, could you see a group of ostensibly avant-garde artists not only addressing the crowd, but making fun of their own avant-garde art while doing it? For 30 years, the band shaped the outer limits of sound—noise, free improvisation, modern classical—into something like rock music, bridging the visionary impulses of experimental art with the naive zeal of punk. No other band presided over so many developments in underground music: the evolution of punk and No Wave into what we now call “indie“ (the mid-to-late ‘80s run of Evol, Sister, and Daydream Nation), the alt-rock and grunge boom of the years that followed (1990’s Goo and 1992’s Dirty), the retreat into experiments (the SYR series) and final maturation into something like classic rock for ears weaned on noise (2006’s Rather Ripped and 2009’s The Eternal). They could be brutal, but they could also be pretty—a deference to tradition that, ironically, only made them seem more radical: What could be more confrontational to an art snob than a guitar anthem (“Teen Age Riot”)? And while their gender equanimity was inspiring (they had two frontpeople, Moore and his former wife, Kim Gordon), the real progress lay in how they played with it: Moore sounding sensitive and ethereal, Gordon roaring like a nightmare truckdriver; Moore, the head, Gordon, the body. No matter how far out their music got (Goodbye 20th Century), it never felt academic, a feat that brought experimental music down to earth and made rock seem more plausible and limitless than any artist since Jimi Hendrix. Reflecting on their career, Moore said the thing about those cheap thrift-store guitars is that they usually didn’t sound good in regular tunings anyway, at least until you shoved a drumstick under the strings.