Generator-offset property: Difference between revisions
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== Theorems == | == Theorems == | ||
=== Theorem 1 === | |||
Let ''S'' be a 3-step-size scale word in L, M, and s, and suppose ''S'' is | Let ''S'' be a 3-step-size scale word in L, M, and s, and suppose ''S'' is ASWFG. Then: | ||
# ''S'' is unconditionally MV3 (i.e. MV3 regardless of tuning). | # ''S'' is unconditionally MV3 (i.e. MV3 regardless of tuning). | ||
# ''S'' is of the form ''ax by bz'' for some permutation (''x'', ''y'', ''z'') of (L, M, s). | # ''S'' is of the form ''ax by bz'' for some permutation (''x'', ''y'', ''z'') of (L, M, s). | ||
# The cardinality (size) of ''S'' is either odd, or 4 (and ''S'' is of the form ''xyxz''). | # The cardinality (size) of ''S'' is either odd, or 4 (and ''S'' is of the form ''xyxz''). | ||
==== Proof ==== | ==== Proof ==== | ||
Assuming | Assuming ASWFG, we have two chains of generator ''g''<sub>0</sub> (going right). The two cases are: | ||
CASE 1: EVEN CARDINALITY | CASE 1: EVEN CARDINALITY | ||
O-O-...-O (n/2 notes) | O-O-...-O (n/2 notes) | ||
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(The above holds for any odd ''n'' ≥ 3.) | (The above holds for any odd ''n'' ≥ 3.) | ||
Now we only need to see that | Now we only need to see that ASWFG + odd cardinality => unconditionally MV3. But the argument in case 2 above works for any interval class (unconditional MV3 wasn't used), hence any interval class comes in at most 3 sizes regardless of tuning.--> | ||
== Conjectures == | == Conjectures == |