Assistants

composer-nb as a tool for Claude, Cursor or any assistant that speaks MCP: it writes a cell, checks it and draws the sheet.

An assistant can talk about music all day and produce nothing you can hear. Plugged into composer-nb, what it hands back plays: a cell it has checked against the parser, which plays right in the chat in claude.ai and Claude Desktop, and the sheet music as a picture or a MIDI file.

The connection is an MCP server. Once it is connected you write in English, in the chat you already use:

Take The Sound of Muzak, put the hi-hat on every eighth, and bring it down to 80.

The assistant writes the cell, calls parse, and if the parser says line 5: The snare line is 6 steps long, which doesn't fit 12 steps a whole number of times, it fixes the cell before you see it. Then it calls render for the sheet.

Install the plugin

In Claude, the composer-nb plugin brings the connector and four skills: write-cells (parse every cell, fix it, hand it over), groove, practice and theory.

Claude.ai and Claude Desktop. Customize → Plugins → Add → Add marketplace, with the repository pkhambat1/composer-nb. Select composer-nb, then Add. Then add its connector on the plugin’s Connectors tab. The server has no sign-in.

Claude Code.

/plugin marketplace add pkhambat1/composer-nb
/plugin install composer-nb@composer-nb

Connect it

For the connector alone, or another assistant.

Claude.ai and Claude Desktop. Settings → Connectors → Add custom connector, with the URL:

https://composer-nb.vercel.app/mcp

Claude Code.

claude mcp add --transport http composer-nb https://composer-nb.vercel.app/mcp

Cursor, Windsurf, VS Code and the rest take the same URL as a remote MCP server.

Nothing is stored on the server: a request is a cell in, a result out.

Tools

Tool	Does
parse	Checks a cell. Returns the errors with their line numbers, the settings and names in effect, and for each play a grid of every hit and note, bar by bar, with the chords it heard.
render	The sheet music as a PNG (the kit on a percussion staff, each instrument on a staff of its own), or a MIDI file, or the ABC notation.
library	Searches the grooves: transcriptions and harmony to start from, each with its code and its page.
reference	The pages under Language, Drums and Pitched instruments on this site, for the assistant to read.

The reference pages and the grooves are also MCP resources, for clients that read those.

In claude.ai and Claude Desktop’s chat, parse also draws the playground’s own cell under the reply: its code, which you can change and run again with Run or Shift+Enter, and its player. What you play there reaches the assistant with your next message. Ask for an empty cell to write in, and you get one.

What to ask for

• A groove from a description: “seven-eight, hats on every eighth alternating open and closed, kick and snare resolving every two bars.”
• Variations: “the same at 80 with just the hands, then bring it up ten at a time”, each a cell.
• An exercise written out: “a funk groove with the ghost notes on the and of 2 and 4, in 6/8”, as a sheet to print.
• A chord chart with a bass line under it, in a key or a mode, as a MIDI file for your DAW.
• An explanation that plays: “I don’t understand how the ride and the kick line up here”, as a cell of just the ride and the kick.