You're right, bwardmusic, it's in 4/4 the whole time, but what DOES change is the groove. There aren't too many songs that you can pull that off in either, but Tom is just an amazing song writer. Conversations (preferably the version on Access All Areas) is one of my favorites by him. My all-time favorite would have to be Freetime.
I feel a flashback coming on...
I used to record songs from the radio when I was 13 (this would have been 1990, right when I was getting into jazz) and a local jazz station played Freetime. I ran out of tape and never got who wrote the song. I'd say for a good 5 years I was clueless who wrote it, then I started getting into Spyro Gyra. At that time, you couldn't get a lot of the older CD's because MCA quit pressing them, so I only had the newer CD's. Finally Amherst started printing the old ones again, and I went to Best Buy and saw three new CD's I had never seen before (City Kids, Carnaval, and Freetime). I looked at the back of the Freetime album and the first track (the title track) was the same length as the song I had on that tape. I thought, "wouldn't it be crazy if that song was by Spyro Gyra the whole time." That was the longest trip home from Best Buy ever. I got home, held my breath, and when those first 6 bass notes played, I jumped around my basement like I had just won the powerball.
To me, finding music that speaks to you the way Spyro Gyra does is worth so much more than money.