In the key of Em, does the F#m7-5 chord have the b13 (D natural) or the 13 as an available (ex)tension?

Same question in Bb Major regarding the Gm7 chord, is the 13 (E natural) an available (ex)tension?

If so, why??

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    @ToddWilcox Sorry for my poor english..english isn't my first language.What I mean is the tension note for the chords like 9th 11th 13th. Notes you could add on the chords. Commented Feb 27, 2018 at 17:43
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    @Tim Actually doing a search for "tension note" helped me a lot. Now I understand the question. Commented Feb 27, 2018 at 17:54
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    @tim - how about changing it to color tone ?
    – Stinkfoot
    Commented Feb 27, 2018 at 17:58
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    @everyone Tension is term used at Berklee to describe extensions to the chord. "The word "tensions" is really short for "extensions" because they are an extension of the basic seventh chord." - thejazzresource.com/chord_tensions.html
    – r lo
    Commented Feb 27, 2018 at 18:56
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    @rlo - funny, because 'ex' in English at least usually means 'used to be'. Funny...
    – Tim
    Commented Feb 27, 2018 at 20:25

1 Answer 1


For half-diminished 7th chords, the b13 is an available tension and the natural 13 and the #13 are not available (technically the #13 is just an octave above the 7th so it's not a tension in this case). So for the F#m7-5 chord, D natural is available and D# is not. The reason why the b13 is available in this case is because the 5 is diminished, which means the b13 is two steps away from both the 5th and the 7th.

For minor 7th chords, the natural 13 is an available tension, the #13 is enharmonic to the 7th (an octave up) and the b13 is unavailable. So you could use E natural for the Gm7 chord. The reason why the b13 is unavailable in this case is because it is only one step from the 5th. The 13 is two steps from the 5th and only one step from the 7th, but it works better to be closer to the 7th than the 5th in this case.

See: http://www.thejazzpianosite.com/jazz-piano-lessons/jazz-chords/available-tensions/

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  • Not up to speed yet ! F#m7-5 with a D note makes D dominant 9, without a lot of 'tension'. Missing something - unsure what...
    – Tim
    Commented Feb 27, 2018 at 18:06
  • @Tim If the F# is the lowest sounding note and the D is above, it could be heard as an F#m7-5addb13. "Tension" in this case is meant in a different sense from the typical sense of a feeling in the listener. This is a branch of jazz chord theory that seems to be sort of "grass roots", you might say, where a tension is a note you can add to a 7th chord to add flavor. But some tensions "work" better than others. Available tensions are 9ths, 11ths, or 13ths that "work" and unavailable tensions are the same intervals that "don't work". Maybe a bit simplified but it's a way to view it. Commented Feb 27, 2018 at 18:12
  • @Tim I suggest following the link, which explains it better than I can. Commented Feb 27, 2018 at 18:13
  • I see that the page you linked to points out that these available tensions are the ones which are used in practice, but does not rule out that other tensions might be used too. Just to add some information, here is a question about adding a ♭9 to a major 7th chord. I flipped through my copy of Ted Greene's compendious Chord Chemistry, and found a few examples of Maj7(♯9) chords listed, but none for Maj7(♭9) chords, and none for Maj7 with sharp or flat 13ths.
    – user39614
    Commented Feb 27, 2018 at 18:39
  • @DavidBowling Good point. My answer is intended to address what seems to be the nature and context of the question, not a general guideline of what intervals can or should be added to chords in jazz. And sounds like both the asker and I could benefit from reading Ted Greene's book. Commented Feb 27, 2018 at 18:44

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