Curt has a great article up about career changes, and I particularly like the way he frames up "dual-tracking..."

While you continue on your current path, identify parallel steps you can take that will move you in the direction you want to go. For example, that could be networking and building the relationships you need, developing an expertise, taking classes, etc.

I've been doing a lot of this kind of planning with my clients lately -- identifying ways to grow the music part of their income while slowly closing out old "day job" commitments. Some of our plans even involve running three or even four tracks over the VERY long haul...