Have you ever heard the term diatonic harmony before? …..Some of you are probably staring at your computer or mobile device blankly, others may be like “ehhh isn’t that when a ship comes down and…” Just kidding. Some of you may know exactly what it is, but if you don’t or you need a better understanding then continue reading. It will greatly help you in your jazz journey as you continue to progress.
What is Diatonic Harmony
Diatonic harmony is a fancy way of saying chords or notes that relate to a certain key. For example, the note D is diatonic to the key of C because it can be found in the C major scale. As you might be thinking, “Well it can also be found in other scales too.” Yes it can, so it is also diatonic to those keys as well. Notes and chords can be diatonic to more than one key, only when you are not analyzing the degree of the note or chord. So what does that mean? If you analyze the note D as the 2nd degree of the C major scale, it will only be the 2nd degree of the C major scale. There will not be any other keys in which the note D is the 2nd degree of that scale. This holds true for chords as well. In the key of C, the ii-7 chord, ( D-7) is only diatonic to the key of C when it is analyzed as a ii-7 chord. If you are not analyzing the chords, then yes it can also be diatonic to other keys such as Bb and F. Make sense? Hopefully. Let’s keep going.
Diatonic Chords within Keys
We know that a chord can be diatonic to a couple of different keys only if it is not analyzed. When it is analyzed, it only belongs to one key. For each key, there are 7 chords that set a consistent pattern and always serve as the same quality in every other key. I’m almost positive I lost a lot of you just now. Let me show you an example. The notes from a scale are used to build chords so lets start in the key of C. We are going to use all the notes from the C major scale to build chords off of each degree of the scale. Here is the C major scale in case you forgot.
In order to build a chord we are simply going to stack thirds from the scale on top of the 1st degree of the scale, ( the note C). Another way to think about it is, to use the 1st degree of the scale, then skip a note in the scale, then use the 3rd degree of the scale, then skip another note, then the 5th, skip, then the 7th. So we have the degrees 1,3,5,7. We just created this chord using the notes from the C major scale.
The 1st degree of the scale is the root of this chord so we will call this chord I Major 7. We will now move to the D in the C major scale and build another chord the exact same way, by stacking thirds, or skipping notes from within the scale, which ever is easiest for you to conceptualize. If we stack thirds on top of D, only using notes from the C major scale, we get D, F, A, C, which gives us a D-7 chord, or we also call this a ii-7 because it is built off the 2nd degree of the scale.
Now, I won’t type out all the rest of the chords because this would take forever and frankly I’m sure you would get bored, as would I, so here is a picture of all the chords in the key of C.
Notice how we analyze the chord based of the degree of the scale it is built from. In every key the chord qualities of each chord will be the same, meaning the 1 is always major, the 2 is always minor, the 3 is always minor, and so on. Obviously the notes will change because we are using a different scale now to build the chords.
Why is this helpful?
Alright so what is the point of knowing all this? When you are playing a tune, you need to know how a chord fits in with the harmony of the piece. What is it’s function? It’s like knowing how a verb works in a sentence or how a noun works. If you don’t know these things there is now way you’re going to be able to write properly. You might say, “I store the went to.” This makes absolutely no sense. It’s the same thing with music. If you can understand the function of each chord then you are going to be able to construct harmonies, take them apart, and have true freedom over the music.
I don’t want to complicate things further so I will leave you just that. For practice see if you can find the diatonic chords in other easy keys such as F, or Bb. If you are brave, maybe try some keys like Gb or B natural. You’ll definitely have fun with those.
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