I was always more of a Rick Wakeman fan, but Keith Emerson was a must listen for any aspiring keyboardist. The big analog synth solo at the end of Lucky Man was always one you had to learn. Still, I think my favorite ELP track was their take on Copland's "Fanfare for the Common Man", with Karn Evil 9 a runner up.
The Moog, which was state of the art at the time cost tens of thousands of dollars, if not more. Nowadays, any synth from about $700 up can accurately replicate those sounds. However, the basis for all synthesizer programming is still basically unchanged from the early Moogs: attack, decay, resonance, waveform. When my musician friends ask me what it's like to drive the Sprite, the analogy I always use is that it is like playing an early Moog synthesizer: Very basic but VERY fun to play. Even though modern keyboards can do everything an early Moog could do and do it better, there's still something about your first gen analog synthesizers that gives them character.