If an improviser wants to move beyond the basic jam session tunes (e.g. C Jam blues,, Bye Bye Blackbird, Satin Doll) it will be necessary to develop dexterity in more than the usual keys (C, Bb, F, G, Eb). Ultimately the soloist should be able to play equally well in all 12 keys. We have seen through this series that it is very common for jazz standards to use a familiar key in the "A" section, but then move to a distant key at the bridge. This can lead to "bridge phobia" where players panic at the bridge and hope somebody else will take over there.
Most instrumentalists spend their formative years playing only in the familiar keys. This builds a muscle memory that makes the less-used keys feel completely awkward. The only way to solve this imbalance is to practice all the keys equally. This exercise is a simple 8-bar progression, repeated 12 times, following the circle of fourths through all 12 keys. Namely, the form is 8 bars in concert C, 8 bars in F, and so on through Bb, Eb, Ab, Db, Gb, B, E, A, D, G, and back to C.
The changes in each 8-bar section are:
| I | ii V | iii vi | ii V |
| I | ii V | iii vi | I7 | (... on to next key a fourth higher)
The 8 bar progression is based on the major scale and is set to a relaxed tempo of 100 BPM, making this about the easiest 12-key study possible. Nonetheless it is challenging for all but the strongest improvisers. Here is a demonstration to help you understand how the exercise works: