chords_function.csv / chords_tensions.csv。
progression 是 Roman 序列收合連續重複後的 n-gram（n=2..4），門檻 ≥3 次且 ≥2 首歌。
比較相同抽象進行下，Jacob 在不同曲目實際下了什麼 voicing。Roman + chord_type come from chords_function.csv / chords_tensions.csv.
Progressions are n-grams (n=2..4) of the Roman sequence after collapsing consecutive repeats, with thresholds ≥3 occurrences and ≥2 songs.
Compare what voicings Jacob actually plays across songs sharing the same abstract progression.