Source Structures & Modes

In Tessitura we talk about  Structures .  A Structure is any set of 3 or more notes so, scales, triads, sevenths chords, quartals are all  Structures .

Since rotating a structure’s graph around the circle gives us the different modes of the first structure, we organize these structures in a set :  Source Structure + Modes of the Source.  Any of the modes could be considered the  source structure  and it is totally arbitrary, but the  most-often-used  structure (or best-known) is usually considered the  source .

i.e. The  Ionian or Major  scale is considered a source structure.  Dorian, Phrygian, Lydian, Mixolydian, Aeolian  and  Locrian  are all modes of the Ionian (the source structure)

Note: the Ionian is still considered a mode, you can call it the source mode if you wish.

Symmetric Structures

When a structure presents symmetry over transposition, the amount of modes are less than the amount of notes and therefore the structure could only be transposed into a limited amount of keys.

i.e Here’s the  Messiaen IV n3  scale which has 8 notes but only 4 possible modes and could only be transposed into 6 different keys without repeating the set of notes.

You may check our demo videos on symmetric structures over the circle of fifths in our  mDecks Music YouTube channel

Bi-Triadic Hexatonic Structures

This type of structure is composed of two non-overlapping triads.

i.e. The structure that is composed by  two major triads ; on the I (root) and the bII (b2) is an  Hexatonic scale

Since most of these structures do not have a standard name, we have used a simple cataloging system to name them.

The name consists of  HexaTonic  plus the  Roman numeral where de triads appear in the structure  separated by a  :

The structure cards will show the Bi-Triadic Hexatonic symbol (which consists of two overlapping triangles inside a circle) for structures of this type

Note: These structures are of interested since their sound is derived from the amalgamation of two triads. Triadic sound is very powerful and easy to recognize. Bi-triadic structures may be used in composition, arranging and improvisation with great success. Now you have them all, organized and ready to load and study in Tessitura Pro.

Also notice that any mode of a Bi-Triadic Hexatonic scale will also be hexatonic

Tessitura Pro by  mDecks Music