# 243/242

(Redirected from Rastma)
 Ratio 243/242 Factorization 2-1 × 35 × 11-2 Monzo [-1 5 0 0 -2⟩ Size in cents 7.1391196¢ Names rastma,neutral third comma Color name 1uu1, lulu 1sn,Lulu comma FJS name $\text{A1}_{11,11}$ Special properties superparticular,reduced Tenney height (log2 nd) 15.8437 Weil height (log2 max(n, d)) 15.8496 Wilson height (sopfr (nd)) 39 Harmonic entropy(Shannon, $\sqrt{nd}$) ~1.66275 bits Comma size small S-expression S9 / S11 open this interval in xen-calc

243/242, the rastma or the neutral third comma, is an 11-limit (also 2.3.11 subgroup) comma with a value of roughly 7.1 cents. It is significant in Just Intonation as the amount by which a stack of two 11/9 neutral thirds fall short of 3/2 just perfect fifth, by which a stack of two 33/32 quartertones falls short of an apotome (2187/2048) as well as the difference between 11/9 and 27/22, and, the difference between 45/44 and 55/54. The last makes the theory where the rastma serves as the subchroma that separates greater and lesser 11-limit chromas – a theory that becomes especially useful when one works extensively with high-fidelity renditions of the 11-limit.

## Temperaments

Tempering it out in the full 11-limit leads to the rastmic temperament, enabling rastmic chords, or, in the 2.3.11 subgroup, the neutral temperament, enabling neutral chords.

### Rastmic

Subgroup: 2.3.5.7.11

Comma list: 243/242

Mapping: [1 1 0 0 2], 0 2 0 0 5], 0 0 1 0 0], 0 0 0 1 0]]

POTE tuning: ~11/9 = 350.5254, ~5/4 = 386.1653, ~7/4 = 968.6464

Optimal ET sequence7d, 10, 14c, 17c, 24, 27e, 31, 41, 58, 72, 130, 202

### Neutral

Subgroup: 2.3.11

Comma list: 243/242

Sval mapping: [1 1 2], 0 2 5]]

Gencom mapping: [1 1 0 0 2], 0 2 0 0 5]]

Gencom: [2 11/9; 243/242]

POTE tuning: ~11/9 = 350.525

RMS error: 0.3021 cents