There are triads (3 notes), 7th chords (4 notes), 9th chords (5 notes), 11th chords (6 notes), 13 chords (seven notes).

Is there some commonly used term that is used only to describe the quantitative property of a chord. Something like arity..

It seems incorrect to use term "type" for it, because "type" also defines the qualitative properties of a chord (intervals between chord notes).

  • 11th and 13th chords more often than not don't play all the notes they could. With 11ths, the 9 is missed, with 13ths, the key notes are 1,3,7 and 13. - not an answer, thus a comment. I think I asked a similar question some time ago.
    – Tim
    Commented Apr 24, 2019 at 13:26
  • Yes I now that commonly only 4 of the chord notes are played. Commented Apr 24, 2019 at 13:35

3 Answers 3


As an extension of Michael's reference to post-tonal music theory, in that realm we refer to the cardinality of sets. A tetrachord, for instance, is a set of cardinality four, meaning that there are four pitches (or pitch classes) involved. A pentachord has cardinality five, etc.

Although this terminology is typically reserved for post-tonal music theory, I have heard individuals refer to a tonal sonority of cardinality x.


As @user45266 says 'tetrad' etc are logical choices, but they aren't commonly used.

Common practice classical music on the whole just used triad, seventh chords, and to some degree ninth chords. In terms of quantity concepts like arity or sets I think the traditional musical terms is voice or part as in four part harmony, etc. Bach's famous two and three part inventions are an example of the usage. I think it would be perfectly acceptable to say something like 'four voice chord' or 'five part chord.' The meaning should be clear.

However, traditionally a large number of parts - like five part harmony - would often involve octave doubling of tones. This loops us back around to common practice harmony. The triad really is the 'default' chord is some seventh chords and fewer ninth chords. If you want to un-ambiguously convey n-voices of unique pitch classes, four-voice, five-voice, etc. will not be absolutely clear.

You may be interested in these mathy music terms: tertian for chords built of thirds, and quartal and quintal for chords built of 4ths and 5ths.

Tetrachord is a common term, but paradoxically it typically refers to a scale-like set of tones rather than a tertian chord.

Pitch set is a musical term and it has all the quantifiers you are looking for, the only potential down side to that term is its association with atonal music. Not that association with atonal music is a negative (that's a joke) but the only musicians who are likely to be familiar with set theory terminology are those with a lot of academic training.


Not certain of any specific term besides the "-ad" system.

Basically, two-note chords are dyads (whatever you want to say about two-note chords). Three are obviously triads. Four, I imagine, would be a tetrad.

Down the list, we have:

  • monad
  • dyad
  • triad
  • tetrad
  • pentad
  • hexad
  • heptad
  • octad
  • nonad
  • decad

Thanks to Wiktionary for that list. Not super-useful, though, outside of academia. Most of the time, people say "n-note chord" (except "triad", which is such a common theory term that everyone uses it). I'd consider a ninth chord to be a pentad even if it's only voiced with 4 notes, but I don't know how others feel about that.

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