Pink Floyd's David Gilmour and Roger Waters are almost as famous for their feuding as they are for their music -- and although they were bandmates for nearly two decades, their personality conflicts precluded true collaboration for many of those years. One notable exception: the No. 9 song on our Top 100 Classic Rock Songs list, 'Comfortably Numb.'

Originally released on 1979's 'The Wall,' 'Numb' is one of only three songs on the album credited jointly to Gilmour and Waters -- and it's telling that the song had an infamously difficult birth, marked by a long-running, heated argument over how to record the verses.

Gilmour, who composed 'Numb' as an instrumental demo while working on his 1978 solo album, wanted the verses to have a harder sound, but he was eventually overruled by Waters, who drew his lyrical inspiration for the track from an experience he had after being shot up with painkillers prior to a Pink Floyd gig.

After Waters quit the band in the mid '80s, Floyd went on to play 'Numb' the way Gilmour had always envisioned it, while Waters subjected the song to his own tinkering, employing an array of special guests (including Van Morrison, Bruce Hornsby, and Don Henley) at various live performances. But it could be said Gilmour had the last laugh, as his solo is generally considered one of the best of the rock era.

And all's well that ends well: In 2005, when Waters, Gilmour, and their former Floyd bandmates Richard Wright and Nick Mason reunited for Live 8, they concluded their set with 'Comfortably Numb' -- and with Wright's untimely death in 2008, it became the final song ever to be performed by the quartet, adding a fitting, albeit terribly poignant, coda to its story.

Skip to: No. 100 | No. 80 | No. 60 | No. 40 | No. 20

Watch Pink Floyd Perform 'Comfortably Numb'