There is a review of a recent Sonic Youth show in the New York Times. Here's a bit of it:
"Has Sonic Youth lost the untethered, nearly sloppy feeling it had in the 1980's, with those billowy passages of improvised overtone noise, guitars in odd tuning and the tribal drums walloping? Has it become sanitized? No. The tightening of the sound has freed Kim Gordon and Mr. Moore in particular. The second half of the show nearly became the Kim Gordon Quintet: she sang song after song with the same coolly chanted recitations that have become more commanding over time. For his part, Mr. Moore began 'Paper Cup' with an old avant-garde idea from the early 50's: the transistor-radio improvisation. (We heard a snippet of a radio review of the movie 'Sin City.') Then he started a solo by caressing his guitar, rubbing it suggestively against his body, holding it in front of his head. Later he was out in the crowd, rubbing the guitar against people in the audience."