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Adding a REAPER + FabFilter Pro-Q 4 Device to ezbeq

The reaper device type pushes BEQ filters directly into a FabFilter Pro-Q 4 instance running inside REAPER, using REAPER's built-in Web Control interface. ezbeq can run on any machine that can run Python (Linux, macOS, Windows); REAPER can run on any Windows/Mac machine reachable over the network (or the same machine).

The REAPER-side script referenced throughout this guide, proq4_apply_filters.lua, lives alongside this page and can be downloaded directly from there. An example ezbeq config is also provided at examples/ezbeq_reaper.yml in the repository root.

What you need

  • REAPER, with FabFilter Pro-Q 4 installed
  • Both machines reachable over the network (can be the same machine)

Step 1: Configure the device in ezbeq's config.yml

Add a reaper1 entry (name is up to you) under devices::

devices:
  reaper1:
    type: reaper
    ip: 192.168.1.50:8080       # the REAPER machine's IP and Web Control port (see Step 2)
    extstate_section: beqbridge  # optional, this is the default
    extstate_key: filters        # optional, this is the default
    timeout: 3                   # optional, HTTP timeout in seconds

Restart ezbeq after saving. You should see a new "REAPER" device/slot show up in ezbeq's web UI.

Step 2: Enable REAPER's Web Control interface

This is what lets ezbeq talk to REAPER over HTTP. On the machine running REAPER:

  1. Open REAPER's preferences: Options → Preferences → Control/OSC/Web.
  2. Click Add, and choose "Web browser interface" from the list (not a plain "OSC" device - this specific one is what exposes the HTTP interface ezbeq needs).
  3. Set a port (e.g. 8080) - this must match the port you used in config.yml's ip: field (e.g. 192.168.1.50:8080).
  4. Leave the local IP as 0.0.0.0 or blank, so it listens on all network interfaces rather than only localhost (needed since ezbeq is likely running on a different machine).
  5. Click OK/Apply.
  6. Allow the port through your firewall on the REAPER machine. On Windows, PowerShell (run as Administrator): 
    New-NetFirewallRule -DisplayName "REAPER Web Control" -Direction Inbound -Protocol TCP -LocalPort 8080 -Action Allow

Test it works before moving on - from the ezbeq machine (or any machine on the network), run:

curl "http://192.168.1.50:8080/_/SET/EXTSTATE/beqbridge/filters/hello"

If REAPER is reachable, this returns without a network error (the actual HTTP response body doesn't matter much here - a connection failure is the thing to watch for).

Step 3: Set up the track and Pro-Q 4 instance in REAPER

  1. Create a track in your REAPER project (or use an existing one) that sits in your BEQ signal path.
  2. Name the track something specific - e.g. BEQ. You'll need this exact name in the Lua script (see TRACK_NAME below).
  3. Add a single FabFilter Pro-Q 4 instance to that track's FX chain. One instance gives you 24 bands, which is enough headroom for any BEQ profile likely to be encountered.

Step 4: Install and run proq4_apply_filters.lua

  1. Copy proq4_apply_filters.lua into REAPER's Scripts folder. You can find/create this folder via Options → Show REAPER resource path in explorer/finder, then look for (or create) a Scripts subfolder.
  2. In REAPER, open the Actions List (? menu or Actions → Show action list...).
  3. Click New action... → Load ReaScript... and select proq4_apply_filters.lua.
  4. With the action selected in the list, click Run (or double-click it) to start it.

The script runs continuously in the background (via REAPER's defer() mechanism) until you stop it or close REAPER - it doesn't finish and exit like a one-shot script. You'll need to run it again each time you reopen the project, unless you set up an auto-start (see note at the end).

Check REAPER's console (the same window ReaScript errors/prints show up in) for a line like:

proq4_apply_filters: initialized (Proq_Instance=1, FX index 0, 24 bands discovered), watching ExtState beqbridge/filters

If instead you see "Track 'BEQ' not found." or similar, see the TRACK_NAME section below.

The three variables you'll most likely need to adjust

These are all declared near the top of proq4_apply_filters.lua as plain Lua local variables - edit the file directly and re-run it (stop the running instance first, or just re-run it after editing; REAPER doesn't require a restart) to apply a change.

TRACK_NAME

local TRACK_NAME = "BEQ"

Must exactly match (case-sensitive) the name of the track holding your Pro-Q 4 instance (Step 3). If you named your track something other than BEQ, change this to match. If it doesn't match, the script will print Track '<name>' not found. and won't do anything else.

Proq_Instance

local Proq_Instance = 1

Which Pro-Q 4 instance on that track to control, if you have more than one loaded (counting from the top of the FX chain: 1 = the first Pro-Q found, 2 = the second, etc). Most setups only need one Pro-Q instance on the track, so the default of 1 is normally correct. If you ever add a second Pro-Q instance for some other purpose and the script grabs the wrong one, change this to point at the right one - the console message on startup tells you which FX index it actually picked.

DEBUGGING

local DEBUGGING = true

When true, the script prints extra detail to REAPER's console on every filter update: - each incoming filter's raw values exactly as received (before any unit conversion), - the received mv_adjust value, - and, after applying, a full readback of all 24 bands' actual current state read directly back from Pro-Q (not just what the script thinks it wrote) - useful for confirming a filter load really took effect.

Leave this true while you're setting things up and verifying everything works. Once you're confident it's stable, you can set it to false to quiet the console down - there's no real performance cost either way, so this is purely about how much console output you want to see.

Testing end to end

  1. In ezbeq's web UI, pick a BEQ catalog entry and load it onto the reaper1 device/slot.
  2. Watch REAPER's console - you should see filter values being received and applied, and (if DEBUGGING = true) a full band readback.
  3. Open Pro-Q 4's own GUI on the track and visually confirm the bands moved as expected.
  4. Try clearing the filter from ezbeq's UI and confirm all bands reset to flat/off in Pro-Q.

Optional: auto-starting the script

By default you have to manually run the script from the Actions List each time you open the project. If you want it to start automatically, REAPER supports a "global startup action" (via the SWS extension) or a project-specific startup action - search REAPER's own documentation/forum for "startup action" for the exact current steps for your REAPER version, since this is a REAPER-level feature unrelated to anything in this guide's scripts themselves.