21/1
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| Ratio | 21/1 |
| Factorization | 3 × 7 |
| Monzo | [0 1 0 1⟩ |
| Size in cents | 5270.7809¢ |
| Name | 21st harmonic |
| Color name | c4z4, quadcozo 4th |
| FJS name | [math]\text{P32}^{7}[/math] |
| Special properties | harmonic |
| Tenney height (log2 nd) | 4.39232 |
| Weil height (log2 max(n, d)) | 8.78463 |
| Wilson height (sopfr (nd)) | 10 |
| Harmonic entropy (Shannon, [math]\sqrt{nd}[/math]) |
~2.20597 bits |
| open this interval in xen-calc | |
21/1, the 21st harmonic, is the harmonic past 20/1 and before 22/1. It is about four octaves and five semitones in size. Used in harmony, it sounds particularly wide: if the lower note is C2, the higher note will be about F6. Think of a soprano and a bass at their extremes. However, it can be approached as a stack of 3/1 and 7/1, making chords like 1-3-21, 1-7-21, or 1-3-7-21.