feat: add Motif Storyboard composition plugin

docs/devath-reference-notes.md

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+# Devath reference measurements
+
+Analyzed the seven user-supplied FLACs in this workspace using their actual audio
+samples. This is signal analysis of the rendered mixes, not a listening-based
+transcription of their melodies or an account of the artist's intent.
+
+![Relative level and spectral attack timelines](reference-analysis/reference-timelines.png)
+
+## Observable contrasts
+
+Approximate reference points from the one-second summaries:
+
+| Recording | Measured pattern | Useful compositional question |
+|---|---|---|
+| Henka | A marked reduction in level/attacks around 2:03–2:35, followed by a strong return; another reduction near 3:57. | What can be withheld so the recognizable idea matters when it returns? |
+| Phantasy | Lower, interrupted activity around 1:27–2:23, contrasting with the stronger regions before and after. | Can a fragment carry continuity across a less active passage? |
+| Blumengarten | An interrupted middle region around 2:02–3:02, then renewed sustained activity; marked reduction near 4:19. | Can the same identity support different densities and articulations? |
+| quiet wish | A broad reduction around 1:53–2:32 before activity returns. | Does a long breath make the return more effective than adding notes? |
+| Light Aspect | A smaller reduction around 1:33–1:49 and a later reduction around 3:04. | Can a shorter contrast work without rebuilding the entire phrase? |
+| Petals | More consistent relative activity through much of the first four minutes, with short dips and a lower closing region after roughly 4:11. | Can development happen with small changes while the groove stays continuous? |
+| VERDICT. remix | Stronger sustained regions roughly 1:01–1:48 and 3:02–3:48, separated by a less active region. | What should remain recognizable across contrasting presentations? |
+
+These times are prompts for human listening, not asserted verse/drop boundaries.
+RMS is affected by arrangement and mastering. Spectral attacks include drums and
+sound-design transients, so neither curve measures melodic note density.
+
+The design inference is to support both subtraction/return and continuous-groove
+writing, rather than force every generated phrase through the same climb and
+resolution. The implementation includes optional fixed groove, fragments, note
+subtraction, different articulations, register return, and section composition.
+This does **not** establish that Devath used those exact note-level operations.
+No source notes or audio were copied into presets or used to train a model.
+
+## Reproduce
+
+```sh
+python scripts/analyze-references.py . --output docs/reference-analysis
+```
+
+Requires `ffmpeg`, NumPy, and Matplotlib. The script decodes mono audio at 11,025
+Hz and uses a 2,048-sample Hann window with a 256-sample hop. It summarizes RMS
+and positive log-spectral flux per second, normalizing each curve to its own
+95th percentile for visibility. Candidate texture changes compare standardized
+low/mid/high-band energy over eight-second neighborhoods, with separated peaks.
+[Raw summaries](reference-analysis/measurements.json) include track durations and
+within-track 80th/20th percentile ratios. Automatic tempo and chord estimates are
+intentionally omitted: coarse onset periodicity and spectral peaks are not
+reliable transcriptions of these full mixes.
+
+A detailed melodic study still needs a listening pass with annotated motifs,
+harmonic rhythm, bass/lead relationships, and returns, ideally checked against
+stems or MIDI. These measurements alone cannot identify exact chord progressions,
+voice leading, emotional meaning, or which sound carries the melody.