Concrete examples of
Trans3ChordClass-
Denotators are written as:
![“Example 2.1” : Trans3ChordClass(t0,t4,t7)
“Example 2.2” : Trans3ChordClass(t0,t4,t7,t10)](../KlangArt99173x.png)
Note that any representative of a
Trans3ChordClass provides suitable coordinates of
the
Trans3ChordClass-
Denotator, i.e., one may alternatively write:
Usually one classifies TwelveToneChords with respect to the Fifth-Transposition t7,
because by recursion one reaches all twelve transpositions. The Colimit of the
corresponding M7-Diagram yields a coarser classification than the M3-Diagram:
In order to obtain a full chord classification with respect to the 48-elemented symmetry
group of the TwelveToneSystem, one has to add two suitable arrows to the M7-Diagram,
loaded with the inversion m11 (multiplication of the Cofactor indices by -1 mod 12) and
fifth circle transformation m7 (multiplication of the of the Cofactor indices by 7 mod
12):
At this point we stop working within the pointing ontology, in order to compare it with
Mazzola’s one. Readers who are not familiar with category theory may skip the rest of
this section and may continue with section 4, such as if
- the Forms and Denotators would still have the prefix
- the Form PiMod12 would still be the
Form TwelveTone
While we have been dealing with the category Sets (having sets as its objects and
set-maps as its morphisms), there is another category of major importance for
Mathematical Music Theory, representing musical parameters and their transformations.
The category of modules Mod, which suits for this purposes, shows a different behaviour
with respect to the universal constructions Limit and Colimit. The Power-construction
does not work at all in this category. A natural way out of this problem is
the consideration of functors F : Mod
Sets yielding