Very nice, as are all your vocals. I don't agree with the previous poster (personal taste) about lowering the key; I think the range is perfect for the effect you're going after. You're probably one of the best singer/songwriters on the board and definitely 'pro' quality.

Constructively, I would do three things:

1) I would have the 'shadow vocal' sitting further back in the mix. Try lowering the volume and adding more reverb (to give it more of a 'wispy' quality). Automated faders are probably needed here - Diki (or someone with more recording experience) could probably tell you how to do this.

2) Get a real sax player to do the sax part.

3) Shorten it by about 45 seconds. As with all tunes, stop it before the excitement starts to subside or it starts to get too repetitious.

Good effort, good voice, good arrangement. Keep up the good work.

chas