San Francisco's most famous string quartet, Kronos, always push the boundaries of what should be the chamber music repertory. As founder and violinist David Harrinton waxed nostalgics during the concert closing their three year residency at the Yerba Buena Center for the Arts this past Friday, he brought up their arrangement of Jimmy Hendrix's Purple Haze: it wasn't "a marketing gimmick" but what they do. Indeed, Kronos has been relentless in bringing new genres and new music, even turning to kickstarter to find fresh scores to put on their stands.

For their concert Friday, they lived up to their reputation, delivering world premieres of pieces they commissioned, artsy sonic collages, arrangements of music from all over the world, and even some, you know, classical music. Over the forty years of the formation (no typo there), they have given birth to hundreds of new pieces and collaborated with musicians of all stripes, so for them, it was just one night at the office, business as usual. Those concerts were the last SF chance to see current cellist Jeffrey Zeigler, the quartet announced yesterday that he'd be leaving to a solo and teaching career, and would be replaced in May with Sunny Jungin Yang.