Butterchurn

MilkDrop-style audio-reactive WebGL visualizer, powered by butterchurn. FastMCP 3.4+ server with a full-screen React webapp and an OSC-ready BPM sync endpoint for mixx-dj-mcp.

How it works

The webapp fills the entire browser window with a WebGL canvas running MilkDrop preset visualizations. The built-in beat generator pulses to the current BPM (default 128). Presets cycle through the butterchurn library — click or use arrow keys to switch.

mixx-dj-mcp integration: Send POST /api/bpm { "bpm": 140 } to the backend at 11124 to sync the visualizer's beat to a DJ set.

Quick start

uv sync
cd web_sota && bun install && cd ..
just serve     # backend on :11124 + MCP HTTP at /mcp

In another terminal:

just web       # Vite dev on :11125

Or use start.ps1 for both at once.

API

Endpoint	Method	Description
/health	GET	Server status, version, uptime
/api/bpm	GET	Current BPM value
/api/bpm	POST { "bpm": 140 }	Set BPM (mixx-dj-mcp sync)

MCP tools

Tool	Description
get_bpm	Read current BPM
set_bpm	Set BPM for visualizer sync

Ports

Role	Port
Backend (FastAPI + MCP HTTP)	11124
Frontend (Vite dev)	11125