have trouble understanding the concept of "modal triads". Some people use terms like Lydian or Phrygian triads, but if you build tertian triads on a Lydian scale you end up with "standard" (major/minor/dim/aug) ones. If you use other triads, like quartal triads for example, you end up with different triads, but not 1-#4-5 (Lydian triad). Thank you.

3 Answers 3


The standard meaning of 'triad' is a set of three notes that can be stacked vertically in 3rds. 1,3,5 of some (7 note) scale.

So it's a bit of a misnomer to speak of the 'Lydian triad' (1-♯4-5) and the 'Phrygian triad' (1-♭2-5). But the terms are generally understood as describing the chords, built on the root of a Lydian or Phrygian scale, that may be seen as stating the essence of those modes. The 'tonic triads' of those modes if you like.

  • Would it make sense to describe them as trichords? Or are these triads literally being used as, say, sus#4 or sus#2 chords?
    – awe lotta
    Dec 25, 2019 at 19:36
  • 'Trichord' has a specific meaning, These chords MIGHT fit it. Without context we don't have any way of knowing how they are being used.
    – Laurence
    Dec 26, 2019 at 1:30
  • According to en.wikipedia.org/wiki/Trichord, "In music theory, a trichord [...] is a group of three different pitch classes found within a larger group." What very specific meaning are you referring to?
    – awe lotta
    Dec 26, 2019 at 22:54
  • 1
    You cut the Wikipedika definition short. "A trichord is a contiguous three-note set from a musical scale". The pitches under discussion are not contiguous within a normal scale. They might be within some other type of pitch set.
    – Laurence
    Dec 26, 2019 at 23:44

So we start of with understanding what I triad is. It's just a 3 note chord and the way we label these triads are with numbers and their relations to the scale degree (the major scale to be precise) for example a C major triad is 1 3 5 (CEG). I'm assuming you understand that so if not type a comment and I'll explain it in more detail.

So if we look a the "modal triads" what we are doing, is extracting the main flavours from the modes themselves and putting them into chord form.

Start with the Ionian Triad. well that's just 1 3 5 (a major triad)

Aeolian or minor triad is 1 b3 5 (pretty standard)

then lets look at a dorain triad. The dorian Mode is 1 2 b3 4 5 6 b7 8 so in the first 5 notes theres nothing different about it from the Minor scale. Meaning you still get a minor triad but you can add a 9th (2nd note) or the 11th (4th note) which you still get from an aeolian triad. Therefore we don't get dorian traids.

Phrygian is different, the scale is 1 b2 b3 4 5 b6 b7 8. So in this, we know we can get a minor triad but looking at it theres a b2. Meaning we can have a triad which is 1 b2 5. Which varys from the sus 2 triad from a minor or major scale being 125.

Lydian is the same but just as a major scale. Having the formula 1 2 3 #4 5 6 7 8. The #4 can be replaced from the 3 giving the lydian triad as 1 #4 5.

Mixolydian doesnt have one.

Locrian is is 1 b2 b3 4 b5 b6 b7 (you could have a feild day with this) therefore we have the diminished chord. Then you can insert a b2 giving 1 b2 b5 or a 4 giving 1 4 b5.

  • Why are you only using the first five notes of each scale to construct triads?
    – awe lotta
    Dec 26, 2019 at 23:04
  • Also, why would you add a 9th or 11th? Wouldn't that no longer be a triad? And if you do use extensions, why not just use the 7th (i.e. for mixolydian -> dominant 7th chord) and even the 13th or 6th (i.e. for dorian -> minor add6)?
    – awe lotta
    Dec 26, 2019 at 23:11
  • Well you need to write the first 5 notes of the scale to construct a triad but I was saying if you add the 9th or 11th (without the third) it doesn't construct a unique chord unlike adding the b9 Dec 27, 2019 at 20:54
  • Why are you only using the first five notes? A triad is any three notes. Are you only including 1-3-5 chords and sus chords?
    – awe lotta
    Dec 27, 2019 at 23:26
  • 1
    Everything is based of the root notes major scale. E.g. notes 6 8 3 would be A C E. being an A minor triad Jan 2, 2020 at 4:39

FWIW, there is other terminology using primary or tonal chords/triads for the I, IV, and V chords and secondary or modal chords/triads for the ii, iii, and vi chords.

That isn't the meaning you ask about, but it seems worthwhile to mention it can mean something else in another context.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.