Richard Strauss, Tchaikovsky, Mozart, Beethoven, Holst, Mussorgsky and many, many others.
Soundtracks from John Williams, and many, many others,
ElO, Styx, Alan Parsons, Pink Floyd, Elton John etc.

Although I'm much more into classical music, I enjoy the complexities of Dream Theatre.

To get that "in the zone" mental feeling, I find I prefer trance music with rolling bass lines and female vocalists with soaring voices. For my money, Delerium is the very best at this, and there are others: Enigma is the most famous, but other artists and groups like Amethystium, Royksopp, Ivy, The Xx, Sneaker Pimps, Olive, and Mono do the trick nicely.

For me, Prog Rock is generally for long-distance driving, because the artists often work in lyrical or musical themes over the course of a whole album, and I like to be able to appreciate how the themes weave and change all at once.

Cal me old fashioned, but the Modern Jazz Quartet always plucks my strings. Jimmy Smith is my other goto groove when I need to stimulate the old squash.

You talking over 40 years ago... my brain now has other fish to fry in that pan. I saw Emerson, Lake and Palmer in their prime. From the Beginning...

For this genre: Pink Floyd hands down

Tangerine Dream.

Radiohead. <3