I could not figure out what I was waiting for, so I bought Jammer Live. Hooking up a music keyboard to my computer is going to take some rearranging. However, you can actually play accompaniment style from a computer keyboard and pointing device. The 25 styles that come with the program are good, but of course I want more. Tools are provided for making user styles.

Knowing me, Gigasample is probably not too far in the future. Then integrating vocal harmony with the styles. :-)