Chord Names

There are lots of different notations for naming chords in music. It's especially bad in jazz, where half of the jazz people use triangles and circles and other shapes which you rarely see in the theory of any other musical genre. I occasionally do recreational music programming, and over time I've started to settle on a notation, which is partly produced here for your pleasure.

One rule is that if you have an odd scale degree in a name, like in ".m13", and it is natural, rather than sharpened or flattened, that implies that every other odd scale degree below it is also present (as a natural degree, or a sharpened degree, or a flattened degree, but it has to be there in some form). The chord .m13 happens to have these scale degrees: (1 b3 5 b7 9 11 3). If you add the 13th degree to a .m7 chord, that's not a .m13 chord, it's a .m7add13.

Actually, the rule is a little more complicated than "write the highest odd natural scale degree for which every lower odd scale degree also appears". One quibble is that you would still write a 7 at the end if there were a suspended 2nd or 4th instead of a 3rd. For example, the chord .maj7sus4 doesn't have a 3rd, but we still write a 7 as if the (1 3 5) scale degrees were all there. This isn't as simple algorithmically as writing .sus4add5b7, but it is a common way of writing chords for musicians, and I want my system to look normal to musicians, and not just systematic. Another quibble is that the chord .7 in standard practice has a b7 scale degree, and chords with natural 7th scale degrees have names like maj7 (for a natural 3rd scale degree) and m-maj7 (for a b3). I didn't make this up. Don't blame me.

Another rule is to list altered scale degrees other than (3 5 7) only after the highest natural odd scale degree which you can write. So for example, the chord with scale degrees (1 4 5 b7 b9 13) would be called .7sus4b9add13. Let's walk through it piece by piece: "7" is the chord name for the flat 7th scale degree "b7". It's one of those complicating concessions I'm making to common practice. It would be easier to call it a b7. There are no natural scale degrees above 7 for which every lower scale degree is also present, so this is some kind of 7 chord, and not a 9 chord or an 11 chord or a 13. After that, we just walk up the chord degrees and we describe anything that hasn't yet been specified in the name: the weird 4th instead of a 3rd, the flatted 9th, and finally the added 13.

It would also be tempting to instead call (1 4 5 b7 b9 13) a .13sus4b9no11, but I've decided against using "no X" and "omit X" in my chord names because that would introduce an unavoidable ambiguity in what name some chords should have.

Here is a list of chord patterns in terms of their scale degrees: https://pastebin.com/H1pjhfr9. There are 135 of them! Not bad. It wasn't made by a program and certainly has a few errors, but it's pretty good. I'll verify all of the entries someday.

What can you do with it? Why you can voice chords! The simplest way is to pick a root pitch, and for every scale degree in the pattern, add a pitch to your chord voicing which is a corresponding number of semitones up from that root. What is the corresponding number of semitones for a scale degree? I'll show you! Here's a Python dictionary:
{"1": 0, "b2": 1, "2": 2, "b3": 3, "3": 4, "4": 5, "b5": 6, "5": 7, "b6": 8, "6": 9, "bb7": 9, "b7": 10, "7": 11, "b9": 13, "9": 14, "#9": 15, "11": 17, "#11": 18, "b13": 20, "13": 21}
Let's do one together. For the chord quality .6add9, the pattern of scale degrees is (1 3 5 6 9). Translating this to a pattern of semitone intervals using the dictionary, we get [0, 4, 7, 9, 14]. Do you see? Like we know that a 9th scale degree is 14 semitones up from the root, because "9" maps ":" to 14 in the dictionary. If our root pitch is Bb2, then the pitches which are 0 semitones up and 4 semitones up and 7 semitones up ... are {Bb2, D3, F3, G3, C4}, which can be verified by sitting at a piano and counting keys or visualizing a piano in your head or doing some MIDI-like modular arithmetic. And now you know the pitches of Bb.6add9 voiced up from a root pitch of Bb2. You're welcome!

Really I just wanted to share my chord patterns. I'm proud of them and their naming scheme. I hope you find as much use for them as I have.

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