Led by Robert Fripp, one of the most revolutionary and cerebral guitarists in music, King Crimson have helped to define and develop both classic and New Prog. It may be Fripp's seemingly unquenchable need to find "the lost chord" that has driven the band through its extreme changes: bombastic, complex and possibly overstuffed '70s "Art Rock" on the one hand, and truly experimental sonic innovation with ties to early punk/New Wave outfits like Brian Eno and Talking Heads on the other. Fripp and co. (the band has undergone so many line-up changes it borders on the ridiculous) also genuinely rock harder than most of their Prog contemporaries - indeed, Yes never wrote anything as aggressive and brutal as Red. Along with Fripp's advances on his instrument, the erratic nature of the band's line-up has been instrumental in the group's artistic progress: King Crimson become whatever is appropriate based on the talents of its members. That, probably more than anything else, is what continues to make the band as exciting and vibrant as they've always been.