http://www.youtube.com/watch?v=VcJ-494PfH0 For the guitar-lovers reading this, there a 2008 documentary film entitled It Might Get Loud, which looks back over the history of the electric guitar with help from Jack White, The Edge, and Jimmy Page - it really is well worth a watch. In it, Page describes Zeppelin's music as "Whisper to the thunder" - a comment that couldn't sum up this next song any better. What Is And What Should Never Be starts off mild and simple, almost like a lullaby you'd sing to your newborn to help him drift off into a weary slumber. However dear friends, this point in the song is where your baby-singing antics should cease - don't make my mistake of continuing through the main riff, ramming up the volume on your Marshall Amp and thrashing along to the rap-like chorus as though your 2-week-old child is about to jump out of his cot and mosh around with you. He won't. He'll cry. Listed just after Whole Lotta Love (don't worry, we'll get to that) on Led Zep's second album, Never Be is one of the songs that started to establish Page's affiliation with the Gibson Les Paul that would soon become his signature guitar both in the studio and onstage. For the way in which it drags us from hard rock to gentle melody in classic Zeppelin style, its place on this Top 10 list is made wholly necessary.