Try importing the midi song into Real Band. This will separate the tracks for you. Delete all tracks except the solo track. Save the file as a midi. Open BB and enter all the cords for the song. Then, import the solo midi file as a melody. Here you can turn it off or on, whatever you like. Select your jazz style of preference and instrument of preference for the melody line and press play. Walla, a jazz solo. Sounds like a lot of work, but it's not.