i saw sonic youth at sonar in 2001 and i was off my face on LSD, it was just an annoying drone in the background.
going back to the spanish rockers theme though, one thing that was noticeable about that festival (sonar) is that you had all these techno hippies and ravers outside the CCCB in the centre of barcelona, sitting and having a coffee in the square while all the old people strolled past and it was all calm and nice. i remember thinking you'd never see that sort of interaction together in england.