[!NOTE] Postfader is an unofficial community project. It is not made by or affiliated with Image-Line.

Postfader connects a local AI client to FL Studio through a small controller script. You can ask questions about the current project, change supported controls, audition a note, or measure audio files without building a custom FL Studio integration.

It includes 37 focused tools:

• 12 tools for reading the open FL Studio project;
• 19 tools for changing supported project settings and checking the result;
• one session control for enabling or disabling those changes without restarting FL Studio;
• one short live-note audition tool; and
• four tools for analyzing exported audio files.

What you can do

Postfader can also inspect and control parameters exposed by native FL effects, VST/VST3/AU effects, and Channel Rack generators. Plug-in support is discovered from FL Studio at runtime rather than limited to a fixed list.

Example requests

“Show me every used mixer track and where it routes.”

“Which Channel Rack instruments are not assigned to a mixer insert?”

“Rename insert 4 to Lead Vocal, set its pan to 10% left, and confirm both changes.”

“Set the tempo to 128 BPM while the project is stopped.”

“Enable write mode for this session, then rename insert 4 to Lead Vocal.”

“Compare my latest bounce with the reference and summarize the loudness,
stereo, dynamics, and frequency-band differences.”

Why use Postfader?

• Stay in the creative flow. Ask for project information or routine changes without hunting through several FL Studio windows.
• Know whether a change landed. Postfader reads supported controls back after changing them and reports the before state, after state, and result.
• Start safely. Postfader connects in read-only mode. When you are ready, ask your AI client to enable writes for the current session—no FL Studio restart required.
• Use the plug-ins you already own. Postfader discovers the parameter surface FL Studio exposes instead of requiring a custom profile for every plug-in.
• Keep it local. Postfader has no hosted service, account, telemetry, or project upload step.

What “verified” means

For a supported change, Postfader:

1. checks the target, value, current session, and any supplied before-state;
2. asks FL Studio to make the change;
3. waits for a later FL Studio update and reads the control again; and
4. reports whether the requested state was actually observed.

This catches a common automation failure: FL Studio or a plug-in accepting a command but ignoring the value.

[!IMPORTANT] A verified result means the control was observed at the requested setting. It does not mean the musical choice sounds good. Writes affect the open project immediately and are not automatically rolled back. Postfader never saves the project for you.

How it works

flowchart LR
    A["Your AI client<br/>(MCP)"] --> B["Postfader<br/>runs locally"]
    B -->|"Virtual MIDI"| C["Universal Bridge<br/>inside FL Studio"]
    C --> D["Your open project"]
    B -->|"Files you choose"| E["Exported audio<br/>measurements"]

MCP is the connection that lets an AI client call Postfader's named tools. Live FL Studio communication travels over one local virtual MIDI endpoint. Audio analysis reads exported files from disk because FL Studio's scripting API does not provide live audio buffers.

Supported versions

Python 3.13/3.14 and Windows ARM64 may need a native compiler for python-rtmidi. Current Windows CI runs on x64.

Quick start

1. Prepare a virtual MIDI endpoint

• macOS: enable an IAC bus in Audio MIDI Setup.
• Windows: create one bidirectional endpoint with the virtual MIDI software of your choice.

Postfader does not install or configure virtual MIDI software. You will use the same endpoint for FL Studio's MIDI input and output.

Launch FL Studio once before installing Postfader so it creates its user-data folders, then quit FL Studio.

2. Install Postfader

macOS

git clone https://github.com/synopsys0/postfader-fl-studio-mcp.git
cd postfader-fl-studio-mcp
./scripts/install.sh

Windows PowerShell

git clone https://github.com/synopsys0/postfader-fl-studio-mcp.git
Set-Location postfader-fl-studio-mcp
.\scripts\install.ps1 -DryRun
.\scripts\install.ps1

The installers create a local .venv, install Postfader, and copy Universal Bridge into FL Studio's controller-script folder. They do not change your AI client's configuration.

You can also install the published Python package:

pip install postfader-fl-studio-mcp
postfader-install-bridge

3. Connect FL Studio

Open Options → MIDI settings in FL Studio:

1. Enable your virtual endpoint under Input.
2. Set its controller type to Universal Bridge.
3. Give the input an FL Studio Port number.
4. Enable the same endpoint under Output and give it the same Port number.
5. Open View → Script output and reload the script.

The script should report ready: MIDI SysEx.

4. Check the connection

macOS

./.venv/bin/postfader-doctor --midi-port "IAC Driver Bus 1" --json

Windows PowerShell

.\.venv\Scripts\postfader-doctor.exe --midi-port "Exact Virtual MIDI Endpoint Name" --json

A healthy connection reports:

• overall: "pass";
• a live FL Studio connection;
• a controller script that matches the installed Postfader version;
• bridge_mode: "read_only"; and
• verified_writes_enabled: false; and
• runtime_write_mode_control: true.

5. Add Postfader to your AI client

Use the included configuration generator so interpreter paths, repository paths, and endpoint names are explicit:

./.venv/bin/python scripts/generate_mcp_config.py --help

.\.venv\Scripts\python.exe scripts\generate_mcp_config.py --help

It can produce a Codex command, Codex TOML, or Claude-compatible JSON. See the client configuration guide for complete macOS and Windows examples.

Claude Desktop users can open the release .mcpb, but the extension does not install the FL Studio controller script or create the virtual MIDI endpoint. Complete steps 1–4 first.

Safe by default

Read-only mode

A normal FL Studio launch keeps Postfader read-only: project inspection works, but project-changing tools do not. Audio-file analysis also works without a live FL Studio connection. This is the recommended mode for exploring a real session.

Write mode

When you want Postfader to make changes, ask your connected AI client:

“Enable write mode for this session.”

Your client calls fl_set_write_mode and must carry an explicit user-present confirmation. Postfader then checks the running controller script, changes only that live session, and performs a second handshake before reporting that writes are available. FL Studio does not need to restart.

Ask the client to “disable write mode” when you are done. The setting is never stored in your project or AI-client configuration, and an ordinary controller script reload or new FL Studio process starts read-only again. Use a blank or disposable project the first time you try writes.

Additional safeguards include:

• enabling writes requires an explicit user request and is exposed to MCP clients as a destructive capability change;
• writes to the Master track require explicit permission;
• if the installed controller script and Postfader version do not match, writes are blocked;
• writes are never automatically repeated after a lost or ambiguous response;
• supplied session and before-state checks can reject stale decisions;
• only one local Postfader connection can use the selected virtual MIDI bus at a time; and
• the controller script never calls FL Studio's save-project function.

See Tool contracts for the exact behavior of every write.

Plug-in support

Postfader can work with any mixer effect or Channel Rack generator whose parameters FL Studio exposes to controller scripts. That includes native Image-Line plug-ins and many VST, VST3, and AU plug-ins.

Compatibility is intentionally honest:

• an unfamiliar plug-in can be inspected without first adding it to Postfader;
• a parameter that FL does not expose cannot be controlled;
• very large parameter maps are scanned with explicit limits;
• a write that FL accepts but ignores is reported as unverified; and
• named options must use the exact label FL Studio reports, ignoring case.

See Plug-in support for parameter discovery, option searches, scan limits, troubleshooting, and the community evidence format.

Important limitations

Postfader cannot currently:

• add, remove, or reorder plug-ins;
• reliably control an effect slot's bypass or wet/dry mix;
• hear FL Studio's live output;
• render, export, or save a project;
• decide whether a mix sounds good; or
• turn raw Playlist selection endpoints into a safe automatic render range.

Audio tools analyze files you explicitly select or recent bounces found in bounded FL Studio folders. They return measurements and comparisons, not audio samples or artistic judgments.

The local virtual MIDI bus is shared and unauthenticated. Use Postfader on a trusted, single-user workstation.

Privacy

Postfader itself runs locally and has no telemetry or cloud service. It does not store your projects, recordings, stems, presets, exports, or live-session evidence in this repository.

Your AI client is a separate application and may send tool arguments and results to its model provider. Audio results can include file paths, hashes, and measurements, but never audio samples. Review your AI client's privacy policy and Postfader's security policy before using sensitive projects.

Documentation

Development

Run the safe, hardware-free test suite from the source checkout:

./.venv/bin/python scripts/run_safe_tests.py

.\.venv\Scripts\python.exe scripts\run_safe_tests.py

The safe suite prevents real MIDI access even when ambient environment variables request it. Any live hardware test must use a blank, unsaved project, and its logs, screenshots, and run notes must stay outside the public repository.

License

Postfader is available under the Apache License 2.0. See NOTICE for attribution details.