I vibe-coded this with Claude Opus 4.5 and I'm kind of blown away. It's a browser-based DAW where you describe music and Claude composes it using an agentic loop with lots of tools (create tracks, write notes, read back what it wrote, apply swing, humanize timing, set panning/volume, etc.). It also supports recording via MIDI keyboard, looping, multi-track, panning, a bunch of synth instruments, all inspired by the Logic Pro UI.

I guess Opus 4.5 can build genuinely complex semi-novel multi-step tools now. The whole music engine, scheduler, and tool system came together way faster than I expected. Took maybe four or five days over Christmas break?

You have to provide an Anthropic API key but it's all local to your browser and never goes to my servers. But you can import and export projects, export .WAV, etc. to get around the local storage limitation.

- https://youtu.be/vgeN_obkg50

- https://synthesizer-steel.vercel.app/