1216/1215
| Ratio | 1216/1215 |
| Subgroup monzo | 2.3.5.19 [6 -5 -1 1⟩ |
| Size in cents | 1.4242979¢ |
| Names | password, Eratosthenes' comma |
| Color name | s19og2, sanogu 2nd, Sanogu comma |
| FJS name | [math]\text{d2}^{19}_{5}[/math] |
| Special properties | superparticular, reduced |
| Tenney height (log2 nd) | 20.4947 |
| Weil height (log2 max(n, d)) | 20.4959 |
| Wilson height (sopfr (nd)) | 51 |
| Harmonic entropy (Shannon, [math]\sqrt{n\cdot d}[/math]) |
~2.40674 bits |
| Comma size | unnoticeable |
| S-expression | S16 / S18 |
| open this interval in xen-calc | |
1216/1215, the password or Eratosthenes' comma, is a 19-limit (also 2.3.5.19 subgroup) unnoticeable comma. It is the amount by which 19/15 exceeds the Pythagorean major third (81/64), or 20/19 falls short of the Pythagorean minor second (256/243). It is also the difference between 19/18, the undevicesimal semitone and 135/128, the major chroma, and in addition, between the undevicesimal comma and the schisma.
Commatic relations
This comma is the difference between the following superparticular pairs:
- 76/75 and 81/80
- 136/135 and 153/152
- 190/189 and 225/224
- 256/255 and 324/323
- 352/351 and 495/494
- 361/360 and 513/512
- 456/455 and 729/728
- 676/675 and 1521/1520
- 1156/1155 and 23409/23408
It factors into the following superparticular pairs:
- 2431/2430 and 2432/2431
- 2080/2079 and 2926/2925
- 1729/1728 and 4096/4095
- 1540/1539 and 5776/5775
- 1225/1224 and 165376/165375
Temperaments
By tempering out this comma is defined the eratosthenes temperament, which enables the eratosthenes chords. EDOs supporting this temperament includes 12, 29, 41, 53, 65, 77, 87, 94, 99, 106, 111, 118, 130, 140, 152, 159, 183, 193, 205, 217, 270, 282, 311, 323, 364, 400, 422, 581, and 692.