A practice idea for developing jazz improvisational skills

I've recently started pursuing a practice idea for developing the ability to improvise over a jazz tune. When I take a solo, I have a tendency to rely too much on muscle memory and the layout of the instrument. I want the solo to be created by my imagination rather than mindless movement of the fingers. Here is the idea:

1. Listen to lots of jazz, especially recordings of jazz musicians playing the tune you are specifically working on.

2. Memorize the melody and chords to the tune.

3. While away from your instrument(s), mentally practice soloing over the tune - imagine your instrument playing the notes with an imaginary rhythm section playing the chords for you.

4. When you have your instrument at hand, do this:

a. Make up a melody for a 1-3 measure chunk of the tune in your head, without playing your instrument.

b. Play the melody you made up in 4a. above on your instrument.

c. Repeat 4a. and 4b. until you're done with the tune.

The purpose of this practice is to develop the ability to compose a solo on the fly - ie. improvise. By composing short phrases at a time, the task seems less daunting.
As a demonstration of this practice idea, I recorded myself doing Step 4 above for the tune Blue Bossa, with a backing part courtesy of Band In A Box. I recorded two guitar parts, panned right and left in the stereo field, so that you can hear the two guitars taking turns playing phrases that I composed on the spot.

Some of the phrases required several practice repetitions and re-recording. This is because I can compose a phrase in my head that does not match anything I've ever practiced on guitar before, and sometimes this phrase does not fit neatly under the fingers. Thus it took me about an hour to record this one-minute track. The aim was not to be perfect - let alone impress anybody - but simply to capture the main gist of the melody I spontaneously composed for Blue Bossa. The other reason I did not clean up all my mistakes on this recording was to document my starting point as I journey down the road of jazz discovery - I can't claim progress without showing where I started.

My September 30,2007 solo over Blue Bossa is now up on my MySpace page.