Also Sprach Zarathustra - Richard Strauss. Specifically the Sunrise section (for obvious reasons). Less obvious, however, is that (I'm pretty convinced), Kubrick picked that song VERY specifically. It's a Tone Poem, supposed to be representative of the Book "Thus Spoke Zarathustra" by Friedrich Nietzche. From the wiki: Sound familiar? I think these are also many of the broad themes dealt with in 2001. I just found this stuff connection by making sure i had the title of the work right. Amazing where your internet travels can lead you. edit: full version of the piece- George Solti and the Chicago Symphony:Much of the work deals with ideas such as the "eternal recurrence of the same", the parable on the "death of God", and the "prophecy" of the Übermensch, which were first introduced in The Gay Science.