REAPER documents plugin replacement as preserving routing, but does not promise automatic parameter-modulation transfer between different plugins. For a synthetic-tone project on Mac, the dependable approach is to record the modulation settings, replace the effect, and rebuild the target assignment.

This walkthrough answers one practical question: how do you keep a repeating volume movement when changing effects? It uses a generated sine tone and two included REAPER effects. The distinction between documented behavior and the workflow recommended here matters: the official guide supports rebuilding modulation, but does not establish a universal cross-plugin transfer feature.

What does REAPER actually preserve during replacement?

The current REAPER User Guide describes replacing an FX while preserving its existing routing configuration. It separately explains parameter modulation and saving modulation settings with FX chains or track templates. These are different operations; the replacement description does not promise to match an old parameter to an equivalent control in a different plugin. See the replacement instructions and chapter 19 in the REAPER User Guide.

The defensible answer is therefore narrower than “everything transfers” or “nothing ever transfers.” Automatic semantic remapping is not documented. Plan to inspect the replacement and rebuild its modulation assignment rather than treating a successful replacement as proof that the movement survived.

For this task, keep three questions separate:

Question What to establish
Does audio still reach the effect? Check routing and the replacement’s input/output configuration.
Is the intended control moving? Inspect that specific parameter and its modulation configuration.
Does it move through the intended values? Check its displayed units, minimum, maximum, and timing.

A moving control alone is an incomplete result. Your concrete target might be “output gain moves slowly between approximately −12 and −6 dB.” That description remains useful after a plugin change because it names the behavior you want to reconstruct.

Prepare a synthetic tone and a clear comparison

Use REAPER on your Mac, plus Audacity if you need to generate the source file. The example changes from ReaEQ’s overall output gain to ReaFir’s output gain. It deliberately avoids transferring an entire filter design: the task is to recreate one repeating level movement.

The official effects guide distinguishes ReaEQ’s overall Gain fader from its individual band gains. It describes ReaFir’s Output Gain as adjusting volume after processing. Those controls provide a sensible pair for this limited exercise. Their availability does not establish identical processing between the plugins. See the ReaEQ and ReaFir sections of the Cockos Effects Summary Guide.

Generate the source file

In a new Audacity project, choose Generate → Tone. Select Sine, enter a frequency of 440 Hz, set amplitude to 0.1, and generate 12 seconds. These are illustrative inputs chosen to make the comparison simple; they are not application defaults. Audacity documents waveform, frequency, amplitude, and duration controls on its Tone reference page.

Export the tone as a WAV file using File → Export Audio…, then bring that audio file into a new REAPER project. Exporting produces an audio file for another application; saving an Audacity project serves a different purpose. Audacity explains this distinction in Saving and exporting projects.

Keep the original WAV unchanged. Use the same item position and playback passage for both versions, and save the REAPER project before editing the FX chain. This gives you a stable reference without relying on a remembered impression of the sound.

Define the movement before changing plugins

Write down the intended behavior first. For this example, use:

  • Source: the same 12-second, 440 Hz sine-tone WAV.
  • Movement: a slow, repeating sine-shaped gain change.
  • Timing: an illustrative repeat rate of 0.5 Hz, or one cycle every two seconds.
  • Range: approximately −12 to −6 dB of output gain.
  • Scope: output-level movement, with no intentional EQ shaping.

The two-second period follows directly from dividing one by 0.5. The range and rate are working targets for this example, not measured results. Describing the target this way makes it possible to judge the replacement without assuming that matching percentage settings produces matching gain values.

Build and record the original modulation

Add ReaEQ to the tone track. Leave its bands without intentional boosts or cuts, and select the overall Gain control on the right side of the plugin rather than a band’s gain control. Start with static gain so you can confirm which control you are about to modulate.

To assign modulation, touch the target control, open Param, and choose Parameter modulation/MIDI link. Enable parameter modulation and LFO; leave Audio control signal and parameter linking disabled for this exercise. Choose a sine shape and adjust the rate, baseline, strength, and direction toward the stated target. REAPER documents parameter selection and these modulation controls in chapter 19 of its User Guide.

Before replacement, make a short settings record. Include the exact parameter name, baseline, LFO shape, speed, strength, direction, phase, and whether tempo synchronization is enabled. Also note any automation envelope or linked controller that affects the parameter. A screenshot can supplement the record, but the parameter name and displayed gain values should remain readable.

Observe several cycles and record the approximate lowest and highest gain values displayed by the plugin. If they miss the intended range, refine the original setup now. Otherwise, you would be trying to preserve behavior that has not yet been clearly defined.

Treat this as a verification procedure to perform in the application. No listening test or measured comparison is asserted here.

Replace the plugin and rebuild the destination assignment

Save a separate project version before replacement. Keep the original version available until the replacement has passed the checks below; it is your reference for both settings and behavior.

Select ReaEQ in the track’s FX chain. Use Replace FX… from the FX context menu and choose ReaFir. Using the menu avoids relying on a keyboard shortcut that may differ with your Mac configuration. The guide describes replacement as retaining routing, so check the resulting audio path before proceeding. See REAPER’s FX replacement documentation.

In ReaFir, choose EQ mode and use a flat adjustment curve for this exercise. Select Output Gain as the destination. The effects guide documents ReaFir’s operating modes, its curve reset control, and its output gain in the ReaFir reference.

Inspect the destination’s modulation window before entering settings. Record anything already present, then configure the chosen target explicitly. Recreate the sine shape and timing from your notes, and adjust the baseline and strength while watching ReaFir’s displayed gain. Use the intended −12 to −6 dB movement as the acceptance target rather than copying percentages without checking their result.

This is manual reconstruction. It preserves your design intent through an explicit destination assignment; it does not demonstrate that REAPER transferred the original assignment automatically.

How to check the replacement and resolve mismatches

Check the result in this order. It keeps an audio-path problem from being confused with a parameter-assignment problem.

  1. Confirm the source plays. Use the original tone item and verify that audio reaches the track output.
  2. Confirm the destination. Inspect ReaFir’s Output Gain, rather than an EQ-curve point or another control.
  3. Confirm the movement. Watch several cycles and compare the displayed gain extremes with your written target.
  4. Confirm the timing. Compare the repeat rate and tempo-sync state with the original record.
  5. Confirm the saved result. Save, reopen the working project, and inspect the assignment again.

If the gain is static, first revisit the selected parameter and the modulation-enable settings. If it moves through the wrong range, revisit baseline, strength, and direction. If its starting position differs, compare phase settings before changing the speed.

If the baseline behaves unexpectedly, inspect automation on the same parameter. REAPER documents that an automation envelope overrides the modulation window’s baseline fader. That condition can explain why adjusting the baseline does not produce the expected result. See the envelope discussion in chapter 19 of the User Guide.

For an existing audio-controlled setup, your record needs more than LFO settings: retain the source channels, attack, release, level thresholds, strength, and direction. For a parameter-linked setup, retain the controlling FX and parameter plus the link’s scale and offset. These settings describe different control relationships, so the simple LFO example should not be treated as a complete recipe for those cases.

Once the rebuilt version is useful, save its FX chain for reuse. REAPER explicitly documents saving modulation settings with FX chains and track templates. A template involving other tracks still needs attention to routing: the guide notes that sends or receives involving tracks outside a saved track template are not included. See the User Guide’s modulation and track-template sections.

For future replacements, keep a small record of the destination’s purpose, timing, and actual value range alongside the project. That turns an uncertain transfer into a manageable editing task: select the new control, rebuild its modulation, and verify the behavior you intended to keep.

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