Amongst my favourite music. If you listen to the epically long songs in their entirety, there's immense enjoyment to be had (by those who like this kind of music).
Repetitive, tuneful melodies. Quadra?
[youtube]http://www.youtube.com/watch?v=NEhM4Iwzff0[/youtube]
[youtube]http://www.youtube.com/watch?v=q25Zx6B5HJA[/youtube]
[youtube]http://www.youtube.com/watch?v=FEbb-qaprtE[/youtube]