Dan Haerle is a good source. I studied with him decades ago.
I posted this on the other place you asked this question about Black Narcissus:
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I listened to this track - what a concept. It had been years... I made some chord alterations in the 'last 8 measures'.
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I don't believe you have the "correct" changes.
Don't necessarily think the Real Book has the right changes - it often doesn't.
I wouldn't say that there is a "key", rather different tonal centers. The third 8 measures?
The tune is in 3-sections, each 8 measures long.
First 8 measures:
|| Abm7 | Bbm7/Ab | Abm7 | Bbm7/Ab | Abm7 | Bbm7/Ab | Abm7 | CbMaj7(b5) || - Or should it be CbMaj7(#11) or CbMaj7(#4)?
Second 8 measures (down a whole-step):
|| Gbm7 | Abm7/Gb | Gbm7 | Abm7/Gb | Gbm7 | Abm7/Gb | Gbm7 | BbbMaj7(b5) || - Or could it be BbbMaj7(#11) or BbbMaj7(#4)?
Third 8 measures:
|| EbMaj7(b5) | FMaj7(b5) | BbMaj7(b5) | CMaj7(b5) | EbMaj7(b5) | FMaj7(b5) BbMaj7(b5) |
B7sus4/G AbM7(#4b9) | BbMaj7(b5) CMaj7(b5) ||
What notes to play a solo over?
Looks like the First 8 one could select notes from the Ab Dorian (i.e., Ab, Bb, Cb, Db, Eb, F, Gb), or find a pentatonic scale from that collection of notes. If you analyze this in the Dorian mode, you have im7 - Abm7, iim7 - Bbm7, IIIM7(+11) - CbMaj7(#11).
Second 8 - Gb Dorian, or some pentatonic. Same analysis as the first 8, but down a step.
The Third 8 - use the notes from Lydian scales based off each of the chord roots (i.e., CMaj7(b5) - C Lydian: C, D, E, F#, G, A, B).
There seems to be two non-Lydian-type chords - B7sus4/G AbM7(#4b9) - at the seventh measure..
ALL of the XMaj7(b5) chords might be best labeled XMaj7(#4).
Use the melody for guidance.
Some will say that each of the first two sections are in some Mode, perhaps so, if it makes it easier to find a
bag-o-notes, go ahead (many do).
Is this worth analyzing as you would a Mozart piece - your call. The 3rd 8 will be difficult. Black Narcissus wasn't composed during the Common Practice Period.
This is more Impressionistic-influence (?).
I do NOT guarantee the above referenced chords. Get the Joe Henderson recording. This is NOT a beginner's piece.
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Someone wrote a paper to get a "doctoral" degree. on this piece (harmony/solo). I should go back to college and pick up a few more degrees.