It's very common in jazz education to encourage a chord-oriented perspective on improvisation. In many ways, this makes a lot of sense and can be a valuable way of analyzing the music. However, it runs the risk of one failing to see the forest for the trees when applied to many tonal jazz standards, where a key-oriented approach provides a better perspective of how everything really fits together. It can also lead to more lyrical, melodic lines that can provide a contrast to lines that outline the chord changes more. Ultimately, I think both perspectives have their place. Obviously, in tunes that are less tonal, the key-center perspective becomes much less useful.
I was thinking about this today and thought it would be interesting to look at the diatonic chords in a key, and compare what notes in the key worked where, to get a global view of the relationships. The results are interesting, I think:
|Green: works |
Orange: mildly dissonant
Red: strong dissonance
What is interesting here is how nearly every note in the key "works" against nearly every chord. In particular, that scale degrees 2, 3, 5, and 6 can be used anywhere. Note that this is 4/5 of the major pentatonic scale. The 7th degree works nearly everywhere (and even the dissonance against the ii chord is fairly mild). If you take 5, 6, 7, 2, 3, then you have the major pentatonic on the 5th degree as being a pretty much failsafe option against any diatonic chord.
|Same as above, but add: |
Yellow: subtle tension