Compositional theory

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A xen music theory or a compositional theory is a framework that governs the way tuning-related elements (intervals, chords, and scales) are used in music, analogous to Western 12edo functional harmony (commonly called "music theory").

Importance

The concept of a compositional theory is distinct from tuning theory in that tuning theory tells you things like

• cent values in a tuning
• what chords, structures, and JI/DR chords (approximations or not, and approximation quality) various tuning systems have
• LCJI is a psychoacoustic effect
• DR is a psychoacoustic effect

These things don't tell you how to write music any more than an understanding of human color vision or the ways colors mix tells you how to make visual art. In contrast, a compositional theory, or compositional theories, tell you how to write music, and there are many valid compositional theories even for the same tuning system. Absent such a theoretical framework, one might unintentionally copy Western frameworks when writing xen music, though using elements of Western 12edo theory in xen music is by no means inherently bad, as long as they're used intentionally.

Examples

Examples of compositional theories:

• Jaimbee's oneirotonic functional harmony (see the oneirotonic article) and other function-based theories
• Vector's porcupine and pajara functional harmony systems created for 22edo
• Xenmodalism, which can be summed as "depict the emotion/scenery/setting/event using the chords or modes you/the listeners associate with the feelings"
• Primodality and scale-based voiceleading

Equal temperaments

Equal temperaments, usually edos, allow for more freedom of movement from one pitch to another compared to other types of tuning systems, so they may require more awareness of a theoretical framework to keep track of it.

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This is how I conceptualize the way notes are chosen in equal temperaments, from least to most freedom.

These levels blend together in small edos, roughly 19 or smaller, due to the relatively few options for notes.

1. MOS with modifications. Notes are either part of a MOS scale or deviate from it with some regularity. This was no problem in complex 12edo music, but it became limiting in microtonal tunings.
2. Aberrismic ternary with modifications. This started with diasem in 2021, allowing a much wider array of expressions to come from edos large enough to support them. This is still my primary approach in large edos (54+) where ternary scales are more plentiful but keeping track of how each interval is tuned can be difficult.
3. Fragmentary. This started with 37edo in 2023. Every scale now represents vague interval logic. Every set of intervals fits together in specific ways. Fragments of this interval logic can be mixed freely for more granular sounds. Tuning systems start to blend together, with specific ways of tempering being felt less strongly.
4. Freeform. Use whatever notes sound right without checking whether they fit reasonably into a momentary tempered lattice. I've never had the confidence to do this.