Solo Composer

The idea

Music notation is a surprisingly deep problem, and I wanted to see if I could build it. Solo Composer is a research project, not a product. Its design is closely modelled on Steinberg's Dorico, down to the way it's organised into modes, because the question I was interested in was how software like that works, not what a new notation app should be.

It began in 2020 as a web app with a Rust/WebAssembly engine. The current version, a native desktop app built with Tauri, has been in development since December 2024.

A score model built on musical rules

Instead of storing notation directly, the app stores musical events (notes, tempo changes, time signatures) and derives what you see by musical rules: where barlines fall, when a note needs a tie across one, how beams group. That keeps the data simple to edit, and the engraving consistent.

Parsing started in TypeScript. After profiling, I moved it to Rust, and a typical score now parses in a few milliseconds.

Rendering and audio

Drawing goes through cached, backend-neutral draw instructions, so scrolling and selection don't recompute the layout every frame. Skia does the drawing natively, with Metal on macOS and OpenGL elsewhere. Playback uses a multi-instrument sampler with expression and tempo control, and the app can host VST3 instruments.

I designed the architecture and implemented the native Skia layer and VST3 hosting with Claude Code.

Built for agents

The running app serves MCP over streamable HTTP on localhost. Every automation action becomes a generated MCP tool, alongside an onboarding tool that explains the domain model and the recommended order of calls. An agent in Claude Code or VS Code can connect and create or edit a score directly.