Can Jev steer music?

# Jev Playground

Can a **System One** model steer music across styles?

[Jev](https://typesafe.ai/blog/introducing-system-one-models-and-jev) (TypeSafe's first System One model) doesn't generate text or notes — it makes fast, typed **classify / score / pick** decisions with calibrated probabilities. This playground tests whether that is enough to steer a composition:

- **Jev** (or an offline stub behind the same interface) decides *only enum labels*: where the tune sings, how fast it moves, what holds it up, then form, key, meter, palette, tempo and dynamics — and, per 4-bar slot, a harmony-book phrase plus per-bar contours. Code expands those into per-bar chords, roles and notes.
- **App code** expands that plan into notes, engraves it (VexFlow), plays it (smplr) and exports it (`.mid`).

Styles on the dial: **Johann Sebastian Bach · Ludwig van Beethoven · Frédéric Chopin · Claude Debussy · Philip Glass · Hans Zimmer · Laufey · Elijah Fox**.

A style earns a face by diverging on the axes the plan can name — register, motion, accompaniment, palette, rubato — not by having a name, and a test holds them to it: every style's most typical plan must differ from every other's on register, motion and accompaniment. A style is a table row plus a harmony book; none of them has code of its own. The four classical styles are measured against committed public-domain MIDI; Glass and Fox against local files that never enter the repository; Laufey and Zimmer have no MIDI at all (see [`docs/ref-midi/public/README.md`](docs/ref-midi/public/README.md#living-artists-acquisition-status)).

## Routes

| Route | What |
| --- | --- |
| `/` | Landing page: links to the demos. |
| `/music/` | The composer described below: Jev picks labels, code writes the notes. |
| `/trolley/` | Absurd troll