One of the biggest problems in teaching jazz improvisation is getting the novice improviser to relax and let the music flow naturally. The problem starts with the improviser's fear of failure whether self imposed or unwittingly imposed by the teacher/director. When I do clinics for jazz bands one of the most frequently asked questions is how to get a student to relax while playing over changes.
My answer usually catches the director off guard. The simple answer is that everybody starts off relaxed until they find out they’ve done something wrong. Then the fear of failure clouds the issue. When a baby is learning to talk we don’t try to teach them grammar and sentence structure immediately. We let them express themselves the way that comes to them most naturally and then we start to shape their language development. How many years of school are dedicated to learning grammar and subject verb agreement? Most kids have been expressing themselves verbally for five or six years before ever hearing about subject verb agreement or the proper use of pronouns.
With that in mind, why would we expect someone learning the language of jazz improvisation to be able to immediately understand it and play? Most young improvisers like kids learning to speak have some experience in communicating with their listeners. Young players should already have some experience with playing scales before trying to improvise. Kids learning speech have sounds to imitate from hearing their parents and siblings talk. The same has to be true about young improvisers, if you want them to learn the language, they must hear the language. Help them develop a discography with players they need to model.
Once you give them the opportunity to listen to jazz players improvise, let them play along with the recording or try to play what they think they’ve heard the improvisers play. Don’t try to edit what they play, let them experiment. It’s from this imitation and experimentation that the fluidity needed for improvisation develops. Once you try to force the student to adhere to the “proper way” to improvise inhibition sets in. An inhibited player will not develop the fluidity or the confidence needed for success in improvisation. If the student is allowed to play in a relaxed setting with you guiding him/her toward the proper way to speak this new language, success will follow.
One of the things I suggest to teachers when I visit schools is that if they are not comfortable improvising bring in an experienced improviser to work with their students. If you don't have access to good, experienced improvisers, buy some of the fine method books and CDs on the market that offer play-a-long opportunities. There are some that even have sample solos performed by professional musicians for the students to emulate.
Of course, having an opportunity to interact with a "real" player is much better than playing with a recording but being able to hear jazz inflections demonstrated whether live or on recording is significant. Several companies have a roster of clinicians/performers who are available by request to visit your school, take advantage of those opportunities. The most important aspect of this is to have the students play. Let 'em play every chance they get. Eventually with some direction, the student will begin to hear what needs to be edited out or added in as they are playing. Just as English teachers don't grade papers until the student has completed putting his/her ideas down on paper, you'll need to wait until the student has finished playing his/her solo before you critique them. As I said earlier, it is very important that they play uninhibited early on.
I use simple melodies working with students to help them develop as soloists. This accomplishes two things. First, they get a "theme" to keep in mind as they develop "variations" that later become crafted solos and most importantly, they learn the importance of form (consider all the songs based on the simple melody “I've Got Rhythm”). Once they are comfortable with melodic form, I can then address harmony and harmonic chord structures. Assuming that early on you had them work on modes, you can now show them how to use the Dorian mode and the Mixolydian mode with the Ionian mode to form the ii-V-I progression. Using the modes, blues scales and chromatic patterns is less intimidating to the student when presented in such a logical sequence. Now you can point out problems they are having resolving to the correct chord or using trigger notes to move through the changes. The problem most teachers and students have is trying to do too much too soon. Most students find it difficult to concentrate on learning the melody, form, chord progressions and patterns at the same time. That would be like trying to jump from simple math to calculus without a thorough progression from one step to the next. How your students progress depends as much on the presentation as on the process of learning. Let ‘em play!