MIDI Setup

MIDI control is available in OSC-1 Oscilloscope and Audio Visualizers. Both use the Web MIDI API. Chrome and Edge work directly; Firefox asks you to approve a one-time site-permission add-on.

First-Time Setup

1. Connect your MIDI device via USB before opening the browser
2. Open OSC-1 or Visualizers in Chrome, Edge, or Firefox
3. When prompted, click Allow to grant MIDI access. In Firefox, approve the one-time site-permission add-on.
4. Your device appears in the app's MIDI settings — OSC-1: Settings → MIDI; Visualizers: Performer Settings → MIDI

If Chrome or Edge does not prompt for MIDI permission, open the browser's MIDI site settings and ensure MIDI access is set to ask. In Firefox, connect the controller before reloading the page; you can review the permission under Add-ons and themes → Site Permissions.

macOS — MIDI Permissions (macOS 13+)

On macOS Ventura and later, your browser needs explicit MIDI permission:

1. System Settings → Privacy & Security → MIDI
2. Enable Chrome, Edge, or Firefox in the list

Windows

Most class-compliant MIDI devices need no extra driver on Windows 10/11. If your device isn't detected, check Device Manager to verify the device is recognized by the OS, and install the manufacturer's driver when the device requires one.

MIDI Learn

The two apps use different MIDI Learn workflows:

OSC-1 — M/O buttons

Small M (MIDI) and O (OSC) buttons sit next to mappable knobs, sliders, and buttons:

1. Left-click the M button — it pulses while waiting
2. Move a control or press a button on your device
3. Done — the button shows the mapped CC number and the mapping is active immediately

Right-click the M button to remove an existing mapping. If you don't see the buttons, enable them under Settings → MIDI → Show MIDI Learn Buttons.

Audio Visualizers — global learn mode

1. Open Performer Settings → MIDI
2. Click START MIDI LEARN — the button pulses while learning
3. Move the hardware control you want to map; the app captures its CC number and channel
4. Click the button again to stop learning

Mappings persist — and travel

Mappings in both apps are saved locally in your browser and restored on the next visit. Both apps can also export mappings to a JSON file and import them again — use this to back up a controller layout or move it to another machine (OSC-1: Settings → MIDI preset export/import; Visualizers: the MIDI settings export/import buttons).

Akai APC Mini MK2

The APC Mini MK2 gets deeper integration in both apps and is detected automatically when connected:

• OSC-1: the Settings → MIDI panel shows APC Mini connection status and a Test LEDs button that plays the startup LED animation to verify the connection.
• Audio Visualizers: Performer Settings → MIDI includes an APC Mini MK2 section with an LED Display Mode selector — spectrum, stereo-vu, spectrum-vu, or preset-grid — controlling what the 8×8 pad LEDs show.

Troubleshooting MIDI

Device not detected:

• Connect device before opening the browser
• Try refreshing the page with the device already connected
• Unplug and replug the USB cable, then refresh

MIDI Learn not responding:

• Ensure MIDI permission was granted (lock icon in address bar → Site Settings)
• Make sure the correct MIDI device is selected in the app's MIDI settings