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Chord Formulas - including common chord symbols

Chord (music) on Wikipedia

Chord formula JSON structure is similar to scale formulas with a couple of additions. "symbols" are the chord symbol(s). Common symbols include:

  • M = major
  • m = minor
  • -, b or dim = diminished/lowered
  • +, # or aug = augmented/raised
  • digits = scale degrees
  • add = added note(s)
  • sus = suspended - missing 3rd

  • or + = raise degree one step

  • b or - = lower degree one step

When there is more than one symbol the most common is given first.

  • "chordSize" refers to the length of the formula - as in scales
  • "formula" is the #steps between the notes of the chord - as in scales
  • "intervals" is the interval between the notes of the chord
  • "chordSize" is the number of notes in the chord

For 13th chords, the 11th is omitted from the formula, intervals, and the spelling.
For example a C13 is C, E, G, Bb, D, A omitting the F.

"formulaNumber" is a 3-byte hex (12 bits) where each bit corresponds to the scale degree-1 of the notes in the chord, with the root note at "C".
So bit 0 = C, bit 1 = C#/Db etc. This is the absolute formulaNumber expressed in hex, meaning pitches are normalized to a single octave range.

"spellingNumber" is similar but uses the actual chord spelling over a 2-octave range.

For example, C Dominant ninth (formula "9") spelling is C, E ,G, Bb, D.
scale degree-1 == 0,2,4,7,10 as binary: 0100 1001 0101 or 0x495 and 1173 decimal. Both the formula number and spelling number are expressed as decimal in the JSON file.

Some of the chords include "drop 5" in the name. This indicates the 5th of the chord
is omitted from the formula and spelling. The reason for this is omitting the 5th
is a common convention in certain types of chords and chord inversions.
The symbol(s) remain the same however.

MusicXML

The resources Chord_Test.mscz and Chord_Test.musicxml provide examples of how chords and ties between chords are represented in musicXML. The first note of the chord has no special XML elements. Subsequent notes include a </chord> element between the <note> and <pitch> elements.

Ties between chords Each note of the chord tied to the same note in the next chord includes notations
and tie elements indicating the start of the tie:

<tie type="start"/>
<notations>
  <tied type="start"/>
</notations>

Each note of the tied chord includes notations and tie elements indicating the end of the tie:

<tie type="stop"/>
<notations>
  <tied type="stop"/>
</notations>