245/242

Interval information

Ratio	245/242
Factorization	2-1 × 5 × 72 × 11-2
Monzo	[-1 0 1 2 -2⟩
Size in cents	21.32964¢
Name	frostma
Color name	luuzzy2, luluzozoyo 2nd
FJS name	[math]\displaystyle{ \text{M2}^{5,7,7}_{11,11} }[/math]
Special properties	reduced
Tenney norm (log2 nd)	15.8555
Weil norm (log2 max(n, d))	15.8733
Wilson norm (sopfr(nd))	43
Comma size	small
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245/242, the frostma, is a small 11-limit comma measuring about 21.3 cents. It is the amount by which 5/2 exceeds a stack of two 11/7's.

It can be factored into (243/242)⋅(245/243) and (896/891)⋅(2835/2816).

Temperaments

Tempering out this comma alone in the 11-limit results in the rank-4 frostmic temperament (→ Catalog of rank-4 temperaments #Frostmic (245/242)), or in the 2.5.7.11 subgroup, the rank-3 frost temperament. In either case, a stack of two 11/7's is equated with a 5/2 major tenth, enabling frostmic chords. It is also used in the construction of the frostburn temperament.

Etymology

This comma was named after Frostburn in 2022. Before it got the name frostma, it was known as the cassacot, probably derived from cassandra and tetracot. However, cassandra was a misnomer for andromeda. The temperament's name was later corrected. Since then, cassacot has lost its root, thus justifying the new name.

245/242 should be the frostma because 243/242 is the rastma…

—Praveen Venkataramana