If you ever need to explain the concept of je n'ais ce quoi to someone, play them a few post punk albums by other artists then play them Daydream Nation. Virtually any adjective you can apply to those bands and those albums - angular, disaffected, dissonant, incendiary, jagged, muscular, sneering, etc - also applies to Sonic Youth, but there's an unidentifiable *more* to SY, especially on Daydream Nation, that those other bands, many of them incredible in their own right, simply do not have.