twelvetake-helix-stadium-mcp 0.2.1

Read, explain, edit, and build Line 6 Helix Stadium (.hsp) presets in plain language — an MCP server.

helix-stadium-mcp

Work with your Line 6 Helix Stadium presets in plain language, without knowing the technical details.

Point your AI assistant at a .hsp preset and ask what it does, how two snapshots differ, or to change it — brighten the lead, add a reverb, set up Rhythm / Lead / Clean snapshots. You get plain-English answers with real values (dB, Hz, ms) instead of raw parameter numbers, and any edits are written back safely. It's an MCP server, so it runs in any MCP client (Claude Desktop, Cursor, VS Code, and others).

Example

Ask "what does this preset do?" and point it at a .hsp. You get the whole signal chain back, per path:

# Dual Rectifier Lead
tempo 120.0 BPM | active snapshot #0
Snapshots: 1. Rhythm (blue), 2. Lead (red)
## Path 1
  [amp] Cali Rectifire — on [per-snapshot] · Drive 7.5 | Bass 5.0 | Master 4.0
  [cab] 4x12 Cali V30 — on · HighCut 9.0 kHz | Distance 2.0 "
  [fx]  Minotaur — on [per-snapshot] · Gain 45 % | Level 60 %
  [fx]  Simple Delay — on [per-snapshot] · Mix 18 % | Time 400 ms | Feedback 25 %

Friendly model names, on/off state (and which snapshots switch it), and every parameter in the units you'd read off the hardware.

Because it understands the whole patch, it can also change it for you. Ask for more gain on the lead or a touch more reverb, and it edits the exact block and parameter — then writes the result back through a safety check (validate → byte-exact round-trip → atomic write with a backup). It can also build a preset from scratch, set up snapshots, and assemble a setlist.

Try asking

• "What does this preset do?"
• "What's different between my Rhythm and Lead snapshots?"
• "Add a Plate reverb after the amp and set the mix to 20%."
• "Give the Lead snapshot more gain without making it louder."
• "Set up Rhythm, Lead, and Clean snapshots on this preset."
• "Build me a clean preset with a US Deluxe amp, a 1x12 cab, and a spring reverb."
• "Find me a plexi-style amp." / "List every delay model."
• "Turn these presets into a setlist for Friday's gig."

What it does

• Reads .hsp presets losslessly (byte-exact round-trip).
• Explains a preset in plain English — the full signal chain of each path with friendly model names, on/off state, per-snapshot & footswitch tags, and parameters in real units (dB, Hz, ms, %).
• Diffs snapshots — exactly what changes between two snapshots (e.g. Rhythm vs Lead), in real units.
• Edits — change parameters in real units, toggle or add / remove / reorder blocks, rename, and set up snapshots, in plain language. Any model in your catalog can be added at its factory defaults.
• Creates — start a new preset from scratch and build it up block by block.
• Assembles setlists — order a batch of presets into a setlist with a pre-gig checklist.
• Browses the model catalog (list / describe / search models).
• Validates a preset's structure (and, with the catalog, its model ids and controller sources).

Every change is written back through a safety gate — validate → round-trip → atomic write with a .bak backup — and HELIX_MCP_READONLY keeps the server read-only whenever you want it.

Install & configure

uvx twelvetake-helix-stadium-mcp serve      # or: pipx run twelvetake-helix-stadium-mcp serve

Add it to your MCP client's config. Most use an mcpServers block:

{
  "mcpServers": {
    "helix-stadium": {
      "command": "uvx",
      "args": ["twelvetake-helix-stadium-mcp", "serve"]
    }
  }
}

If the catalog isn't auto-detected, set HELIX_STADIUM_RES to your install's res/ folder (the one containing P35ModelCatalog.json). Check detection with helix-stadium-mcp doctor.

To keep the server read-only — for instance when you point it at presets you don't fully trust — set HELIX_MCP_READONLY=1, and the write tools are left out at startup.

Tools

Read

Tool	What you'd ask it
read_preset	Load a .hsp and get its structure (paths, blocks, snapshots)
explain_preset	The full signal chain in plain English, with real units
diff_snapshots	What changes between two snapshots
list_models · describe_model · search_models	Browse the model catalog
validate_preset	Check a preset's structure
detect_install	Find the Helix Stadium catalog this reads from

Edit & build

Tool	What you'd ask it
edit_param	Set a parameter, by current value or for a specific snapshot
add_block · remove_block · move_block	Add, remove, or reorder a block
toggle_block	Turn a block on/off — globally or per snapshot
configure_snapshots · set_active_snapshot	Name the scenes and pick the active one
rename_preset · rename_snapshot	Rename the preset or a snapshot
create_preset	Start a new blank preset to build up
build_setlist	Assemble ordered presets into a setlist + checklist

Every write tool goes through the safety gate above; set HELIX_MCP_READONLY to leave them out.

Roadmap

Pre-1.0, following semantic versioning — the tool surface can still change between minor versions.

• v0.1 — read, explain & compare presets; browse the model catalog; validate a preset.
• v0.2 (now) — the assistant makes changes for you: edit parameters, toggle / add / remove / reorder blocks, rename, and set up snapshots; build a preset from scratch; and assemble setlists — in plain language. Every write goes through a safety gate, with HELIX_MCP_READONLY to keep it read-only on demand.
• v0.3 — generate a whole preset from a description.
• v1.0 — a stable tool surface.

macOS support is in progress alongside Windows.

Requirements

• Helix Stadium installed (Windows confirmed; macOS support in progress). The server reads the model catalog and per-model definitions from your own install at runtime.
• Python 3.10+.

Trademarks

Not affiliated with or endorsed by Line 6 or Yamaha Guitar Group.

All trademarks are the property of their respective owners. "Line 6," "Helix," and "Helix Stadium," along with any amp, cab, or effect model names and other brand or product names that appear (for example through the model catalog or a preset), are used here only to identify compatible gear. This project claims no ownership of any trademark it references.

License

MIT © TwelveTake Studios LLC. See LICENSE.