I understand that when playing in a mode, the cadences are quite different from tonal cadences. For example, in the Phrygian mode a cadence would be IV - iii (or II - i if we're renumbering the chords).

Q: What are all of the cadence options for all of the major modes?

Our three major modes are Ionian, Lydian, and Mixolydian. The Roman numerals for these are:

Ionian
I  ii  iii  IV  V  vi  vii°

Lydian
I  II  iii ♯iv° V  vi  vii

Mixolydian
I  ii  iii° IV  v  vi ♭VII


You'll notice that both Ionian and Lydian have a major V chord, meaning that the standard cadence of V–I is possible in these two major modes. (Whether it's the most common, I can't answer.) Perhaps due to Mixolydian's minor v chord, the ♭VII is often substituted as a dominant, resulting in a ♭VII–I cadence.

If we generalize it to all modes, it seems that the hierarchy of cadential harmony goes something like:

1. V where possible (Ionian, Lydian)
2. ♭II where possible (Phrygian) (maybe there's something to be said about tritone substitutions here?)
3. ♭VII where possible (Dorian, Mixolydian, Aeolian, sometimes Phrygian)

The only mode missing here is Locrian, which many (myself included) don't even consider an adequate mode based on the diminished tonic triad.

• If someone is curious about Locrian harmony, this question goes into more detail about it: music.stackexchange.com/q/32420/7222 – Dom Jun 5 '17 at 14:53
• @Dom That answer looks like Patrx2...he is sorely missed! – Richard Jun 5 '17 at 14:56
• Yeah, I know. One thing we can do is point to answers like this when we can. – Dom Jun 5 '17 at 15:04
• Ah yes, the Inadequate Mode. It has so few possibilities, yet I just can't master it. – Areel Xocha Jun 5 '17 at 21:20
• Thanks for the answer Richard. If that's the strategy, would chord subs for those cadential chords also be suitable? For example, ii for Dorian since the ii is a sub for VII since they share many notes? bvii for Phrygian? vii for Lydian? ii for Mixolydian? ii dim for Aeolian? – 02fentym Jun 7 '17 at 1:03