I'm trying to add more detail to what I'm playing by using non-diatonic chords.

So far the main ways I have found are:

  1. Borrowing chords from parallel key (mode mixture)
  2. Chromatic Mediants (playing major chords that are minor thirds apart from example).
  3. Using Secondary Dominants.

Are there any other ways?

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    To get started, google "secondary dominants," "tritone substitutions," "added 6th chords", "Neapolitan chords." There are plenty more options - the question is too broad to answer IMO. The above Google suggestions haven't even mentioned secondary 7th, 9th, 11th, and 13th chords for example. If all else fails, buy a good harmony textbook! – user19146 May 23 '17 at 2:11
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    I would think this exactly the kind of question that this site should have a good answer to, if it doesn't already! I'd imagine we could condense down the most common tactics for adding interest to diatonic-triadic harmony into a sensible length answer. – topo Reinstate Monica May 23 '17 at 6:38
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    @topomorto But the answer to this would be "describe in detail the history of the development of Western harmony over the last 500 years". That's far to broad to give a sensible length answer! Even "simple" (by modern standards) 19th-century harmony textbooks may have 100 pages or more on this topic. – user19146 May 23 '17 at 14:48
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    @alephzero I don't see that we have to describe in detail the history of Western harmony over the last 500 years to give a reasonable answer to the question from the perspective it seems to be being asked from - I think a good answer just has to briefly explain, from a fairly beginner perspective, the most common ways that a tonal piece can venture outside the strictly diatonic. I do agree that a super-detailed answer can't be made in a few lines, but a useful answer can be made in a sensible length. We don't have to close as too broad just because an answer requires a few paragraphs. – topo Reinstate Monica May 23 '17 at 15:10
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    I don't know what "perspective" the OP is asking from, so I've no idea whether an explanation of how William Byrd, J S Bach, Beethoven, Wagner, Stravinsky, or Elliot Carter "added non-diatonic chords" is what he/she wants to know - and you could make just as long and varied a list based on popular 20th/21st century music styles, of course. – user19146 May 23 '17 at 16:59

Disclaimer: I present concepts in an order that’s a bit different from most tonal harmony curricula; I’m trying to give a progression from easiest to most advanced, without all of the other corresponding factors that go into a curriculum design.

This is not an exhaustive list, but I'm happy to make any additions suggested in the comments!

Mode Mixture

Mode mixture occurs when we mix (or "borrow") pitches/chords from the parallel mode into the current mode. This is most easily seen in what we call the "Picardy third," where an ending chord in a minor work is actually a major triad. In the below example, in C minor, we "borrow" the E♮ from the parallel major. We can also conceptualize this as borrowing the I chord, inserting it where we might expect a i chord. (Note: The leading-tone B♮ is standard chromaticism in a minor key, so I'm not including a separate entry on it here.)

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In the following example, in major, I show a clear I--IV--V--I progression in the opening two measures. Note how, after the double bar, I use mode mixture to use a iv chord instead of a IV chord.

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Important: When using mode mixture, the mixture is kept until you reach the point of cadence. If one wanted to add a ii7 chord after the iv in the above example, it should really be a iiø7 to keep the A♭ until the cadence point.

Lastly, the below example is modified from the end of Wagner's Ring cycle; it's an example of mode mixture that was later used as the 20th-Century Fox fanfare.

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To create your own mode mixture, just modify a given chord (or chords) to be the quality they are in the parallel mode. (Another way to think of this: just "borrow" the chord/pitches from the parallel mode.) If you're in major and on a vi chord, just use instead a VI chord, since that's the harmony that's in the minor mode.

The Neapolitan

This is also basically mode mixture, but it's enough of a "thing" that I made it a separate entry. Basically, the Neapolitan is a chromatic variant of the ii chord that's actually built on the lowered second scale degree. It is most often found in first inversion. It typically occurs in minor, but it can occur in minor or major.

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Applied Chords (or "secondary dominants")

Secondary dominants occur when you precede a diatonic triad with its own V or V7 chord. In the first two measures of the below example, I have a simple I--V--I progression. After the double bar, I insert the dominant of the V chord, marked with an asterisk. This D major chord, which is nondiatonic in the key of C major, is labeled V/V and read as the "V of V."

enter image description here

Another type of applied chord is the secondary leading-tone chord. Here, I insert not a V/V, but a vii°7/V. The process is the same: find the chord I'm moving to, and precede it with a vii°7 built on the leading tone of the root of that chord.

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Putting It All Together

Even with just mode mixture, the Neapolitan, and applied chords, we can do some pretty gnarly stuff (listen here!):

enter image description here

I start with a plain old tonic moving to a dominant seventh in first inversion. With the B♭ in the bass I insert an applied chord (in inversion) to the IV that occurs in the second measure. Then I embellish that IV through mode mixture with a iv (both in first inversion).

I reach the dominant, at which point I don't resolve it to tonic, but rather to an A♭7 chord in third inversion (whaaa?!?). This chord is actually an applied dominant to the Neapolitan, which appears on beat 3 of measure 3. Then I move through an applied chord to V at the end of the third measure. I just have a big old dominant in m. 4, and then a cadence in tonic in the last measure.

There are other things I could add in here; augmented sixth chords and tritone substitutions, for instance, but I'll wait and see if the interest is there before I keep going. For now, you might just want to check out my answer at "Punning chord" to get an idea of one clever thing you can do.

  • You might add at least a shout out to augmented sixth chords, perhaps linked to the Neapolitan. – Todd Wilcox May 23 '17 at 21:08
  • Anyone else not able to see the pictures? – DonielF Jun 19 '17 at 3:50
  • I can see the pictures just fine on two different computers and a phone. Maybe try a different browser? I've had that problem in the past. – Richard Jun 19 '17 at 3:56

Determining which non-diatonic chords you can get away with adding to your piece depends on the genre (and sub-genres, whether you're trying to compose in a fusion/crossover genre hybrid, etc.). Richard gave a good list for classical music purposes (19th century common practice period if you ignore tritone substitution)--and I'd like to emphasize augmented sixths in that list further--but other genres can be even more flexible than that.

I tend to think of my non-diatonic harmonic language in 4 camps: classical (19th century common practice period, what I learned in music harmony class), pop, jazz, and heavy metal. (I tend to think of rock as intermediate between pop and heavy metal, but I'm sure there are other camps--there's the 5-tone equal temperament scale in gamelan's slendro usage, for example.)


Use of Modes

Take a stereotypical pop chord progression like vi-IV-I-V. Substitute those chord symbols with those that treat the passage as if it's in the relative minor instead of a major key (so that example progression is i-VI-III-(b)VII). Then figure you can use any of those chords in the home major key and in the same context. Yup, assuming your original key is F major, that's the sound of you using Eb major chords for (b)VII. I find this goes beyond borrowing from closely related minor keys because traditional harmonic functions no longer necessarily apply. This is one of the only ways I've been able to explain the common i-VI-(b)VII-i chord progression, for example.


Tritone Substitution

Got a nice dominant-function tritone (e.g. B-F in C major)? The stereotypical chord you'd use in that scenario is G7, but try Db7 instead today! Got a nice secondary dominant-function tritone (e.g. C#-G as V of V of C major)? You may usually use C# diminished 7th there, but try Eb7 instead!

Altered Chords

Stuff like flat 5, sharp 11, flat 9, minor-major 7ths, flat 13, some combination of any of them, and more are all in a day's work for jazz lead sheets.

These probably aren't all the ways jazz and its sub-genres use non-diatonic chords, but they're a nice start.

Heavy Metal

Unusual Chord Progressions

Some common chord progressions in heavy metal are found in here. This is arguably using modes, but these tend to be different modes from what pop uses. There is a similar loss of traditional harmonic function, though.

Another chord progression I've often found in heavy metal is i-#IV-(i)--two chords with tonics a tritone apart.

Extreme metal sub-genres such as death metal and thrash metal may end up using even rarer chord combinations. Power metal may be more harmonically conservative and stick closer to pop- or classical-like harmonies.

My last paragraph alluded to another tip for learning how to add non-diatonic chords to music--listen to others' works. Hear what chord progressions they normally use when they use those non-diatonic chords. Figure that, if they got away with those chords, you can too.


You can justify just about ANY chord through secondary dominants, mode mixtures. So I'm not sure such justifications have much value.

Don't get stuck on just chords, include the melody. We're in C major. The melody is G, the obvious harmony is C or maybe G7. But what other chord has a G? Maybe Eb major. Try it! Try making that an Eb7 (a Db note in the key of C! Don't panic! :-) Ab seems an obvious move. But we want to stay 'in C'. Can that G persist, making it Abmaj7? And then maybe it's time to come home. Keerp the G melody, give it the obvious G7 chord, home we go.

Are all those chords 'borrowed' from some related or adjacent key/mode? Probably. Bot what makes them work is the melody note they can all have in common.

Don't just write chord sequences, write songs with melodies!