BPScript — A Modern Language for the Bol Processor

BPScript is a research-driven composition language built on the Bol Processor (BP3) — the formal music grammar system Bernard Bel and Jim Kippen have developed since 1981, originally to model North Indian tabla improvisation.

BP3 has an unusually wide range of formal power: depending on which mechanisms are active, its grammar spans context-free (Type 2) to context-sensitive (Type 1) and beyond — a tunable complexity rather than a fixed class. It is also bidirectional: it can generate music and recognize whether a sequence belongs to a musical language (PROD/ANAL modes), a reversibility rarely found in music systems. Forty years of work gave it weighted stochastic grammars, native polymetry, conditional flags, master/slave patterns, seven derivation modes, and dozens of performance-control functions. TidalCycles cites it as an influence.

That power has always been locked behind a dense, archaic syntax and a 1990s C codebase. BPScript is the research effort to keep the formalism and modernize everything around it:

• A readable, typed language — 3 reserved words, 24 symbols, 9 flag operators. Typed temporal primitives (gate, trigger, cv), scenes, actors, declarative I/O mappings.
• Native code via backticks — embed runtime-evaluated code (currently JS / Web Audio) alongside the temporal structure, in a single file.
• Compiles to BP3 — the transpiler emits native BP3 grammar, so 40 years of derivation expertise are reused, not reinvented. The engine runs in the browser via WebAssembly.
• An evolution path — BPx, a next-generation reactive derivation engine designed to succeed BP3's batch C core (see the BPx repository: ../BPx/docs/ARCHITECTURE.md).

Try it online: roomi-fields.com/bpscript — write BPScript, compile to a BP3 grammar, and derive it in the browser.

Setup

git clone https://github.com/roomi-fields/BPscript.git
cd BPScript
npm install

# Run the regression gate (single definition, also wired to pre-push)
npm run verify

Structure

src/
  transpiler/        Tokenizer, parser, AST emitter (compileToBPxAST)
lib/                 JSON libraries — controls, alphabets, tunings, temperaments,
                     octaves, scales, homomorphisms, voices, modulation
test/                Guards and reference grammars
docs/                Specification, design, and reference documentation
public/demos/        Example .bps scenes

Pipeline

Source .bps → Tokenizer → Parser → AST (compileToBPxAST)
                                          ↓
                                   BPx (derivation)
                                          ↓
                                    Timed tokens

The timed tokens are the language's output. A downstream runtime (scheduler, audio, MIDI/OSC) consumes them — out of scope for this repository.

Test

Prerequisite: build the engine with ./build.sh all --archive (see Setup).

The regression gate is three npm scripts, wired to pre-push — a push is refused if any bites:

Command	What it guards
npm run arch	dependency structure + freshness of the bundled libraries
npm run typecheck	types of the digital / homomorphism libraries
npm run verify	AST_SPEC conformance of the whole corpus + tempo operator emission

npm run arch && npm run typecheck && npm run verify

# Complementary suites, run by hand when you touch their surface
node test/scan_corpus.mjs        # BP3 -> BPScript -> BP3 round-trip
node test/voie_b_status.mjs      # comparison against the native baseline, AT THE END OF THE CHAIN

The old S0-S5 staged pipeline (test_all.cjs, runner.cjs, the sN steps) was removed on 2026-07-19. Nothing live invoked it, but it stayed readable and kept being mistaken for the current procedure. See test/README.md.

The 36 reference grammars live in test/grammars/grammars.json. Each stage's snapshots are in test/grammars/{name}/snapshots/.

Detailed results: test/RESULTATS.md Open points with Bernard: test/FEEDBACK_BERNARD.md

Documentation

Start with docs/INDEX.md (full index). Highlights:

• docs/spec/LANGUAGE.md — complete language specification
• docs/spec/EBNF.md — formal grammar (ISO 14977)
• docs/spec/AST.md — AST node reference
• docs/design/ARCHITECTURE.md — compilation pipeline
• ../BPx/docs/ARCHITECTURE.md — next-generation BPx engine (separate repository)
• docs/reference/BP3_FILE_FORMATS.md — BP3 auxiliary file formats
• BACKLOG.md — open points and backlog