Here to share a quick summary and findings from “Chord Quality” menu of “Jazz Standards Statistics“.
For this analysis, each chord root is interpreted as a relative number based on key-signature of the song, also, tensions are ignored. Here are histograms of chords appearing in Major key songs and minor key songs.
Sorry for the squeezed labels due to wide variety of chords appearing in the songs. You can pinch and zoom at the dashboard. Also the dashboard has a function to reduce the number of categories by categorizing several chord qualities into higher level groups like “Major chords”, “minor chords”, etc.
Anyway, let’s have a look on the top 10 chords.
| Major Key Songs | minor Key Songs | |||
| 1 | 5_7 (dominant 7) | (11.5%) | 1_m7 | (13.0%) |
| 2 | 2_m7 | (10.8%) | 5_7 | (11.2%) |
| 3 | 1_△7 (*maj7) | (8.9%) | 1_m (*minor triad) | (9.4%) |
| 4 | 6_7 | (5.4%) | 2_Φ7 (*m7b5) | (5.1%) |
| 5 | 1_6 | (5.0%) | 4_m7 | (4.5%) |
| 6 | 1_7 | (4.0%) | b6_△7 | (3.1%) |
| 7 | 3_m7 | (3.9%) | 1_m6 | (2.9%) |
| 8 | 6_m7 | (3.9%) | b7_7 | (2.9%) |
| 9 | 2_7 | (3.5%) | b6_7 | (2.9%) |
| 10 | 4_△7 | (2.8%) | b3_△7 | (2.4%) |
Findings:
- For both, chords in 2-5-1 progression occupied top 3 (top 4 in minor).
- Non-diatonic chords in Major key top 10 result are 6_7, 1_7, and 2_7.
- Non-diatonic chords in minor key top 10 result is only b6_7.
- Peak at 3_xx chords in Major key is not found in minor key.
- Peak at 6_xx chords in Major key is not found in minor key.
- Peak at b6_xx chords in minor key is not found in Major key.
- Frequency of 2 is almost same as 5 in Major key, but it’s half of 5 in minor key.
From these findings we can have fun creating hypothesis (but not proven).
For example, in Major key, 5 may always approached by 2, and 3-6-2-5-1 progression may occur more often. Meanwhile in minor key songs, 5 is approached both by 2 and b6. Also besides 2-5-1 progression, b6-5-1 progression may occur often.
However, to verify such hypothesis, we should look at statistics on chord progression, which I’ll write an article later on. The dashboard already has implemented “Chord Progression in Major Key Songs” and “Chord Progression in minor Key Songs“, you can jump and verify your hypothesis 🙂
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