Diminished tuning is a system of choosing the reeds for a diatonic wind instrument (such as a harmonica or accordion) in which the blow notes repeat a sequence of
C E♭ F♯ Aand draw notes follow a repeating sequence of
D F G♯ B(perhaps shifted to begin with E♭ and F, with F♯ and G♯, or with A and B).
For example:
| hole | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| blow note | C | E | F | A | C | E | F | A | C | E | F | A | |
| draw note | D | F | G♯ | B | D | F | G♯ | B | D | F | G♯ | B |