I listened to SMiLE to-day as part of my new listening schedule, and I thought the ascending and descending phrases at the beginning of "Mrs. O'Leary's Cow" would be pretty easy to figure out. I was surprised to find that they're actually chromatic and that - while some instruments modulate up a fourth - the organ phrase remains the same.
I used only guitar and organ, but I think the guitar part is also played on piano and bass.