MOS substitution
MOS substitution is a procedure for obtaining a ternary (3 step sizes) scale from two MOS patterns. It consists of taking one MOS pattern (called the template MOS), choosing a step size, and overwriting all instances of that step size using the step pattern of another MOS pattern (called the filling MOS). Unlike MV3 scales, a MOS substitution scale may have any combination of step sizes.
Examples
Many familiar ternary scales (in particular, the nicest MV3 scales such as zarlino and diasem) can be constructed as MOS substitutions.
LMsLMLs <- LLsLLLs x LMLML, LssLsLs x MsMs, sMssMss x LsLLs
LLmLLLs <- LLsLLLs x ms
LMsLM <- LLsLL x LMLM
The three standard diaslen scale patterns, denoted 4sL (LsLsLmLsLsm), 4sC (LmLsLsLmLss), and 4sR (LsLmLsLsLms), may be constructed via MOS substitution, giving generator sequences for the three scales:
| chirality | filling MOS | step pattern | generator sequence | ||
|---|---|---|---|---|---|
| template MOS: | LXLXLXLXLXX
|
intvl. class of gen.: | 2-steps | ||
| 4sC | mssmss
|
LmLsLsLmLss
|
GS(L+m, L+s, L+s) | ||
| 4sR | smssms
|
LsLmLsLsLms
|
GS(L+s, L+m, L+s) | ||
| 4sL | ssmssm
|
LsLsLmLsLsm
|
GS(L+s, L+s, L+m) | ||
