We know that, when each mode is compared to its parallel major scale, it has a unique set of alterations (various degrees of the mode that are sharped or flatted).  Therefore, there are going to be certain chords that each mode complements particularly well because those chords contain the same alterations.  Let’s take a look at some general principles first:

3rds and 7ths:  The “Guide Tones”

The two most important degrees within any mode are the 3rd and the 7th (and, in the case of the rarely-used Locrian mode, the 5th is also a key player).  And take note of the fact that all of our basic chords are built using the root, 3rd, 5th, and 7th.  Again, this is no coincidence.

The Third–Major vs. Minor: Essentially, we want to look at each mode and determine whether the 3rd is natural (indicating “major,” sometimes referred to as a “major third”) or flatted (indicating “minor“, referred to as a “minor third”).  Note that there is no such thing as a “sharp 3rd”–if you raised the natural 3rd by a half step in any key, it would simply be the 4th (because there is only a half step between the 3rd and 4th).

The Seventh:  The seventh also plays a key role, and either appears as a natural 7th or a flatted 7th within a given chord or mode.  Just like the third, there is no such thing as a “sharp 7th”–because if you raised the 7th by a half step, you would simply land back on the root.

The Fifth: Though it only applies to the Locrian mode (and corresponding diminished chords), it is important to note when the flatted 5th appears.  But if you don’t play jazz or classical music, there’s a good chance you’re not going to see it too often.

So now let’s take a look at each mode and, using the 3rd and 7th degrees, we’ll determine what type of chord it suits best.  You’ll notice that there’s some overlap here–some chords work well with a few different modes.  For the most part, you really just have to use your ears and decide what sounds best for whatever situation you’re in.

Ionian mode:  Natural 3rd, Natural 7th

• major triads
• maj7 (and maj9, maj11, and maj13) chords
• 6th chords, 6/9 chords, add9 chords

Dorian mode:  b3, b7

• minor triads
• m7 chords (and m9, m11, m13 chords)

Phrygian mode: b3, b7

• minor triads (for a more exotic sound)
• m7 chords
• NOT m9 or m13 chords (the b2 and b6 in the Phrygian mode would clash with the notes in these chords).

Lydian mode:  #4

• major triads
• maj7 chords (also maj9)
• maj7#11 chords (#11 is effectively the same thing as #4)

Mixolydian mode: b7

• major triads
• dominant 7 chords (and dom. 9, 11, and 13)

Aeolian mode: b3, b7

• minor triads
• m7 chords

Locrian mode: b3, b5, b7

• diminished triads
• m7b5 chords