Classical music also keeps me intellectually stimulated...
Example: Fourth movement of
Brahms Symphony No. 4.
The entire movement is assembled as a series of variations on the very first 8 bars as the original theme. In fact, more than 30 short variations each of which lasts exactly 8 bars will be presented successively without any other stuffing passages till the very end. It is truly amazing to see that Brahms could not only modulate the mood and content of the original theme so drastically in each succession, but also manage to construct the whole movement like a musical story entirely from these 8-bar elements, which include everything from a sobbing monologue by flute solo to a brass chorale to a thunderous outcry of full orchestra. I almost cry when I realize the quality and density of intellect that had been injected into this short 10-min movement.
[the Windows Media sample of 4th movement at the link above contains the theme and first 4 variations... Enjoy!]
