To link FX parameter in REAPER to an MIDI signal (typically, coming from a MIDI hardware), you can either use the system provided by the FX if it has one, or you can use REAPER generic MIDI Linking feature. It is simple: you click a parameter, you choose “Learn”, you move a MIDI controller, and they will be associated. You can customize few extra things like relative and absolute mode, basic offset and scale (these are in another window) and few things, but it is pretty basic.
Natively, you can also map MIDI to actions. Some can inspect MIDI input values and change their behavior accordingly, which can allows you to map MIDI to track properties like volume (it will be action Track: Set volume for selected tracks (MIDI CC/OSC only) in this case).
But what if you need more control? Like, for having volume of tracks linked to MIDI controller, but max-out at 0db instead of +12dB ? Or for linking one MIDI controller to several parameters, and to FX on different tracks? Or to do some maths on the parameter linking? Or for having a particular MIDI hardware to be set as input mapping, excluding the others? Or even going further, by linking any kind of input signal (MIDI, OSC, Keyboard etc…) to any kind of target (FX Parameter, Track properties, Actions, et) from a single unified place?
This is where Helgoboss came into play, by releasing a free VST for REAPER to enhance its external controls and linking abilities (with MIDI/OSC in particular). From the words of its creator:
[ReaLearn] mission is to equip REAPER with the most comprehensive and well thought out MIDI/MCU/OSC learn features that one can imagine (…).Helgoboss, on Realearn.com
ReaLearn has so much features and different use cases that it would be extremely hard to cover everything it can do, so let’s see how I use it: I have a faulty pedal MIDI Controller (FBV Express MKII), which send frequent random MIDI signal (between 0 and 5) when set a minimum position, which prevent using the native linking feature. With ReaLearn, I can adjust the mapping to ignore the values under a certain range. Problem solved!
I was able to push my linkings further so my pedal controller now control several FX at the same time, for eg, a pitch shifter and a EQ, to make some kind of advanced Whammy pedal, with mix control and synced low-pass. Being able to adjust the various output ranges for the linking is what made this allows possible.
Because it is a VST, we can save the mappings as regular FX presets and switch from one to the other quickly, which is extremely convenient. You can also export them, and even generate them from code with variables etc, which is very powerful if you have tons of MIDI mapping to prepare.
So yes, it doesn’t looks fancy (no colors etc), but it is quite ergonomics and efficient this way IMHO. Though, as it has a lots of different features, it might worth looking at a tutorial first. Helgoboss has made some very detailed videos to show you the main concepts and features.
ReaLearn is a solid project, well maintained since 2016 with regular updates via Reapack, and an extensive support. I invite you to consider answering the Helgoboss call for donations to sponsor his work, as we are extremly lucky to have such tools available for free. His generosity goes even further, as it has released the Rust language library he has developed for making ReaLearn, reaper-rs, open source as well. Really high level coding skill! He also made another REAPER extension, but this is a story for another time. 😉
I only scratched the surface, so it can do so much more so… Have fun experimenting ReaLearn! 🖖
Feature Image Credits: Helogoboss