If you've ever wanted to improvise, here's your chance - everyone goes crazy for about two minutes then regains consciousness.

This was Led Zeppelin’s only top 10 hit (No. 4) on the singles charts, and what I like about it is the aleatoric section at letter G, which is more powerful than any classical conservatory-inspired music of the second half of the twentieth century. When will the classical guys understand that one must recapitulate just as their 19th century forefathers did? I like this arrangement in two tempos: very fast or very slow. Take your pick.