I'm looking through a piece of music that has two flats in the key signature. It feels like it's in D minor (the last chord), and the verse alternates between E♭9 and Dm6.

A couple of things - why would the arranger use that key signature? Would the E♭9 be a tritone substitute for what could easily be A7? Could it actually be in a mode instead?

It's Dizzie Gillespie's Night in Tunisia. I've played it with one flat, which somehow makes more sense than 2.

  • 1
    Duuude! please post the name & composer, if not an image of the chart! Jan 15, 2020 at 14:30
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    The clue was enough for jazzers! A Night in Tunisia. Dizzy.
    – Tim
    Jan 15, 2020 at 14:32
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    We're supposed to guess what the music is, why? Jan 15, 2020 at 14:45
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    @MichaelCurtis - no, I didn't want to fall foul of the rule 'what key is this in?' and lose the question. Eb9 and Dm don't feature in many (any?) keys, so the question was based on that. Lots here will have played it many times.
    – Tim
    Jan 15, 2020 at 14:48
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    For a site that often votes to close stuff for being too vague or broad, to not include all the info and leaving hard to find clues for the users to find seems strange to me. Can you please edit the question to include more info so maybe it is helpful to others in the future?
    – b3ko
    Jan 15, 2020 at 14:51

2 Answers 2


Without judging whether it appropriate, I think the reason someone might use two flats in the key signature is the Eb7 chord of the vamp and the E flat at the end of the first part of the melody...

enter image description here

...could be considered to come from the Phrygian mode rather than tritone substitution/altered dominant harmony.

If a tritone substitute is considered clearly identifiable only when part of a descending fifth progression, then it seems reasonable to say the Eb7 chord here is not a tritone substitution, but a chord rooted on the lowered second degree of Phrygian.

In other words iim7b5 bII7 i would be a clear case of tritone substitution, bII subs for V, because it substitutes in a progression of three roots by descending fifth. But just alternating bII7 i bII7 i is not the clear substitution within a descending fifths progression pattern.

So, if someone took that view - the Eb7 is not a tritone substitution - the chord is diatonic to Phrygian (at least the base triad), the Phrygian key signature reinforces that idea.

When the tune gets to using a dominant rooted on A at end the phrase, and it has a proper leading tone, that doesn't contradict Phrygian, not in the classical sense, so that seems like additional support for Phrygian.

Either way it doesn't change what's happening tonally. It's a little like when Baroque scores would use zero flats for D minor. The sharps and flats in the score make the final determination of tonality.


I think the E♭9 is the "foreign" chord here. So i think the piece (hard without having seen the whole piece) is correctly in D minor, with the E♭9 possible a tritone substitute.

I think you were on the right track, but if you can share the whole piece, then i can get it right 100%.

  • D minor has one flat. So that's not the answer Jan 15, 2020 at 14:31
  • @CarlWitthoft - we know that!! What I want to know is some reason why the arranger thought 2flats more appropriate. To me, it's in Dm, (with 1 flat), so don't dv this answer!
    – Tim
    Jan 15, 2020 at 14:43
  • @Tim I didn't DV Jan 15, 2020 at 16:11
  • @CarlWitthoft - answer - or question?
    – Tim
    Jan 15, 2020 at 16:32
  • @Tim either so far as I recall Jan 15, 2020 at 16:43

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