Hello HornFreak,
Although there is nothing like playing with a live band playing the correct chord changes etc we have to do the best we can when we are practicing improvising alone.
One very good tool that can easily be tweaked to various styles of music as well as chord changes and other variable is Band In A Box.
http://www.pgmusic.com/
Just as an example sometimes I set it for an acoustic piano rhytmn section on the Lyle Mays setting and it imitates the style of Pat Metheny. I can plug in the chords and tempo and blow over the chord changes for as long as I want.
There are style settings for Miles, Herbie, Wes, etc etc. Just plug in the chords: Dmi7 | G7 | Cmi7 | etc etc - press play and you are jammin.
This program has actually developed into quite a tool for professional composers, and writers. If you want to play along with the standards it is very easy to find most of them in band in a box (biab) format.
I also like the acoustic trio setting with the upright bass setting. It's pretty amazing what you can do with that program. Excellent for backing practice tracks.
Check it out.
have fun!
don
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