This little tool for jAlbum will help you adding music to any of your albums made with jAlbum. Download the attached zip file and extract to C:\Users\[username]\AppData\Roaming\jAlbum\Tools directory on PC, Applications /jAlbum/[Right-click: Show package contents]/Java/Tools folder on Mac.
The tool is using Jeroen Wijering‘s excellent MP3 flash player. See the original site here. Please read the legal and licencing issues before using it.
Before you add music you might want to compress it to make fit for web use. A reasonable compomise between bandwidth and quality is around 92kbs/Joint Stereo. You can use iTunes or some other free encoder (from here).