It's been a busy week here. I've published 15 more pages in my "taking-me-longer-than-expected-to-finish" Jazz Pianist's Ultimate Guide To The Real Book. One of the newest pages is for the tune Lady Bird, which is a great example of how we can compose new melodies upon pre-existing chord progressions.
In this case, Lady Bird is actually the "pre-existing chord progression." The tune was written by Tadd Dameron, who is a jazz pianist definitely worth checking out. Dameron was active during the bebop period of the 1940s and 50s, although he really wasn't a bop pianist himself. He was a consummate composer and arranger and his piano playing leaned more towards block chords and riffs, but his rhythmic concept fit in perfectly with bebop, which is why so many beboppers liked playing his tunes. Indeed, Lady Bird is one of the first Real Book tunes you should learn.
So along comes Miles Davis, who wants to compose his own tune. Instead of coming up with a new chord progression, Miles decides to use the chords to Lady Bird and write a new melody on top of them. (This is perfectly legal, by the way, since you can't copyright a chord progression. Otherwise, there'd be only one 12-bar blues song!)
So Miles sits down and composes another bebop classic, which he calls Half Nelson. The technical term for a melody that uses an older chord progression in "contrafact," although I can't bring myself to use it in a jazz context. It just doesn't sound idiomatic to me!
Spend a few minutes listening to both tunes, and pay particular attention to how the melodies are different but the chords are basically the same. Then, if you like, sit down at the piano and write your own melody, using these same chords. Who knows... you may write the best song of your life!
Here are the 2 pages: