2. Tuning scheme
The tuning scheme that I use for 10-hole diatonic (Richter) harmonicas (that is, blues harps) is called 19-limit Just Intonation (JI). As described in Theory of harmonica tuning, it is a variant of JI that gives reasonably good chords in both 2nd and 3rd position. The scheme can be summarized as a table (Table 8B in Theory of harmonica tuning).
| Table 1: 19-limit JI for 2nd and 3rd position (deviations in cent from 12TET) | ||||||||||
| Channel | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
| Blow note | 0 | -14 | 2 | 0 | -14 | 2 | 0 | -14 | 2 | 0 |
| Draw note | 4 | 2 | -12 | 4 | 1 | 6 | -12 | 4 | 1 | 6 |
This scheme is essentially that recommended by Pat Missin [Missin, 1996]. The 1st position tonic blow chord is in perfect JI. The tuning of the draw note in channels (holes) 6 and 10 makes it a a major whole tone and a perfect fifth in 2nd and 3rd position, respectively, that are in perfect JI. The tuning of the draw note in channels 5 and 9 is a compromise. It is a little too sharp for the flattened seventh chord in 2nd position and a little too flat for the minor third in 3rd position. However, a positive side effect is that the minor chord in 4-6 draw is accompanied by a difference tone equal to the root of the chord but two octaves down [Missin, 2004].
In addition to the above tuning scheme I use an octave stretching of 2 cent/octave. This means that 2 cent are added (subtracted) for each increase (decrease) of the notes by an octave. I also use a master tuning slightly higher than the standard A4 = 440 Hz, usually A4 = 443 Hz. These adjustments are described in Theory of harmonica tuning and are easily done with the tuner I am using (see next section).