KO-II Controller — MCP Server

Control your Teenage Engineering EP-133 K.O. II with AI via the Model Context Protocol.

Connect Claude (or any MCP-compatible AI) to your KO-II over MIDI — play patterns, compose beats, improvise melodies, and send transport commands — all from a conversation.

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Requirements

• macOS 26+
• Xcode 26+ (or Swift 6.3+ toolchain)
• A KO-II connected via USB

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Installation

# 1. Clone the repository
git clone https://github.com/xhiew/koii-controller
cd koii-controller/KOIIController

# 2. Build the release binary
swift build -c release

# 3. Note the binary path — you'll need it in the next step
echo "Binary: $(pwd)/.build/release/KOIIController"

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Setup with Claude Desktop

Open (or create) ~/Library/Application Support/Claude/claude_desktop_config.json and add:

{
  "mcpServers": {
    "koii-controller": {
      "command": "/path/to/koii-controller/KOIIController/.build/release/KOIIController"
    }
  }
}

Replace the path with the actual output from step 3 above. Restart Claude Desktop.

Setup with Claude CLI (Pro plan)

If you use Claude via terminal (claude CLI), add the server with:

claude mcp add koii-controller /path/to/koii-controller/KOIIController/.build/release/KOIIController

Verify it was added:

claude mcp list

To remove it later:

claude mcp remove koii-controller

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Usage

Once connected, talk to Claude naturally. Some examples:

Connect to the device

"Connect to my KO-II"

Claude will call list_midi_outputs to find your device, then connect_device automatically.

Play a drum beat

"Play a 2-bar techno beat at 130 BPM"

"Make a lo-fi hip hop groove with ghost notes on the snare"

Play a melody

"Play a sad melody in D minor, slow tempo"

"Improvise something uplifting in C major over 4 bars"

Transport control

"Start playback"
"Stop"

Using prompts

The server includes two structured prompts accessible in Claude:

• beat_generator — provide a genre, BPM, and number of bars. Claude will design and play a full drum kit pattern.
• jam_session — provide a mood, key, and scale. Claude will improvise a melodic phrase, optionally with a drum backing.

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Available Tools

| Tool | What it does | |------|-------------| | list_midi_outputs | Lists all MIDI ports on your Mac | | connect_device | Connects to a MIDI port by name | | disconnect_device | Disconnects the current device | | transport_start | Sends MIDI Start (resets to bar 1) | | transport_stop | Sends MIDI Stop | | transport_continue | Resumes from current position | | play_pad | Triggers a single pad (groups A–D, pads 1–12) | | play_drum_pattern | Plays a text-grid drum pattern | | play_key_mode | Plays a melodic sequence using scale degrees | | list_available_scales | Lists the 11 supported scales |

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KO-II Pad Layout

Group A  MIDI 36–47    Group B  MIDI 48–59
Group C  MIDI 60–71    Group D  MIDI 72–83

Within each group:
  <G>.  = base note     (e.g. A. = 36)
  <G>0  = base + 1      (e.g. A0 = 37)
  <G>FX = base + 2      (e.g. AFX = 38)
  <G>1  = base + 3      (e.g. A1 = 39)
  ...
  <G>9  = base + 11     (e.g. A9 = 47)

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Tips

• Drum patterns: each character = one grid step. Never use spaces for visual alignment — they count as rest steps. Use . instead.
• Melodies: the default octave is 5 (matching KO-II's hardware default). Use degree values (1-based) — the server resolves them to MIDI notes automatically.
• Scales: ask Claude to list_available_scales before composing melodies — there are 11 options including pentatonic, blues, and chromatic.
• Tempo: always specify BPM so note durations are calculated correctly.

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Credits

Inspired by mcp-koii by @benjaminr — a Python-based MCP server for the KO-II that sparked the idea for this Swift implementation.

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