The Free Music Archive, run by WFMU, is a database of music that is free to download. Some of the artists additionally allow further distribution and reuse.
Using this fantastic resource, I found the track “As Colorful as Ever” (by Broke for Free), which is available under the Creative Commons Attribution-NonCommercial license. I then synced this up to my voice recording for the White Alice Script, which is also available under the same license, in Garageband.
The mixed down .mp3 version is available for use under Creative Commons, Attribution-Noncommercial 3.0 License.