I'm playing an Jazz improv for the song Summertime and I'm seeing chords that say A-11, Ab13#11, and I just want to make sure I understand the 13#11 chord.

So, In the key of C, a C13#11 chord would be:

C13#11 has C, E, G, Bb, D, F#.

1, 3, 5, b7, 9, #11

In Jazz the default is b7 so that is why it is flat.

Is this correct?

I did a search and there were some similar questions but I'm in a bit of a hurry so forgive me if this is a duplicate.

  • 1
    You left out the 13th, A, in your question but @Aaron included it in his answer. Mar 25, 2021 at 4:23

2 Answers 2


(This has to be a duplicate, but I'm not finding it, so...)

Yes. C13#11, as a complete chord, is spelled:

C E G Bb D F# A

In scale-degree terms:

1 3 5 b7 9 #11 13


The default 7 in that chord will be ♭7, but not every 7 chord (in jazz or anywhere) will automatically be ♭7.

As Aaron points out, the notes constituting C13♯11 are C E G B♭ D F♯ A. You haven't said what instrument you're playing, but it'll be either piano or guitar. On the latter, there's a problem immediately! 7 notes to play, only 6 strings! The saacrificial note is usually the 5, so that G can go. Then you need to try to voice the other notes, with C underneath, as it's the root, so the whole chord sounds good.

On piano, it's a tad easier, as you can spread out more easily. If the G stays, it doesn't want to be next to the F♯, and similarly the A/B♭.

You could of course consider that chord as a polychord - it's effectively C7 and D major mixed. With another player, it could be played as two separate chords.

  • I've got just one note to play (at a time). I play the Trumpet. :-)
    – PatS
    Mar 25, 2021 at 22:05

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