The L42 Transform
L42 on C, voice by voice: the chords it pairs, the voice that steps, the source's own words, and every chord each side spells.
On C, L42 pairs Cmaj7 (C E G B) with Em7 (E G B D): 1 voice steps, 3 hold, and the lead costs 2 semitones.
| Voice | Becomes | Step |
|---|---|---|
| C | D | +2 |
| E | E | holds |
| G | G | holds |
| B | B | holds |
What each side spells
- Cmaj7: Cmaj7
- Em7: G6, Em7
The paper's printed cycle through all 51 chords takes this step 4 times.
As the source prints it
The most parsimonious transformations exchange two types of sevenths moving just a note by a semitone or a whole-tone.
L42 : [x, x + 4, x + 7, x + 11] ↔ [x + 2, x + 4, x + 7, x + 11]
— A Generalized Dual of the Tonnetz for Seventh Chords: Mathematical, Computational and Compositional Aspects, pp. 301–308; Sonia Cannas and Moreno Andreatta. The source, read 2026-10-25.
Rank every pairing of Cmaj7 and Em7 in the calculator · Every chord one voice from Cmaj7