43/32
| Interval information |
prime harmonic fourth
reduced harmonic
(Shannon, [math]\sqrt{nd}[/math])
[sound info]
43/32, the quadracesimotertial harmonic fourth or prime harmonic fourth, is the octave-reduced 43rd harmonic. It is a wide fourth close to those of 7edo and 26edo, and is the first octave-reduced harmonic that is a diatonic fourth. The "prime" in the name "prime harmonic fourth" can be taken both as referring to the fact that it is a prime harmonic and to the fact that it is the simplest octave-reduced harmonic that generates 5L 2s, the diatonic mos. It is sharp of the perfect fourth (4/3) by 129/128.
Approximation
Due to its complexity, this interval is sensitive to mistuning. Nontheless, it is tuned somewhat acceptably in 7edo at 2.768 ¢ sharp, but increasingly better edo approximations are 17\40, 20\47, 23\54 and especially 26\61, where it is less than 0.05 ¢ flat, though some reasonable less accurate tunings in yet larger edos are 29\68 (< 0.25 ¢ sharp) and 32\75 (< 0.5 ¢ sharp), with good approximations becoming very noticeably more frequent in edos above this size.