The Harmonic Shell Model: An Octave-Shell Occupancy Descriptor as a Control for Spectral Processing

The Harmonic Shell Model introduces a dyadic, octave-shell representation of harmonic-index space and investigates the occupancy of the highest significant shell as an explicit control descriptor for spectral processing. Valence, the accompanying Harmonic DAW prototype, implements the framework as a real-time spectral audio effect. Version 1.1 is an implementation-synchronised release. The paper now describes the outer-shell occupancy descriptor exactly as implemented: significant harmonic support is detected relative to a tracked fundamental, restricted by the active ELEMENT count gate, and evaluated independently from the sequential-fill reference trajectory. This preserves the central distinction between count-derived shell filling and support-derived occupancy. The current Valence implementation organises harmonics into dyadic shells and applies a family of explicitly analogy-based chemistry- and nuclear-inspired DSP transformations. These include ELEMENT-based harmonic occupancy, a bipolar REACTIVITY macro combining outer-shell emphasis and intra-shell spreading, harmonic-lattice attraction through ELECTRONEG, odd/even stereo organisation through SPIN, temporal DECAY of upper partials, isotope-inspired inharmonic stretching, FISSION and FUSION spectral mappings, and alpha/beta/gamma-inspired decay behaviours. SNAP additionally allows the tracked fundamental and resulting harmonic lattice to be constrained to a musical scale and root. The narrow research question is whether outer-shell occupancy in harmonic-index space provides useful control or explanatory information beyond conventional spectral descriptors such as harmonic count, spectral centroid, slope and flatness. Its interpretation as a perceptual “stability” dimension remains a testable hypothesis rather than an established result. Version 1.1 also clarifies the boundary between physical inspiration and musical construction: the atomic and nuclear terminology supplies an organising vocabulary for DSP operations and does not imply simulation of atomic or nuclear matter. The release contains the technical research note together with the current Valence JUCE-independent DSP core, Harmonic DAW processor wrapper and editor source headers. Version: 1.1Version DOI: 10.5281/zenodo.22675845Previous release DOI: 10.5281/zenodo.22409312