Historical clue formulations

• Three-note chords — 2025-04-30
• Three-tone chords — 2021-04-07
• Common chords — 2020-07-19
• Basic chords — 2020-05-02
• Common chords — 2013-04-28
• Threesomes — 2002-08-09
• Many chords — 1998-12-13