MIDI triggering in Propellerhead Reason

In this guide, you will learn how to use MIDI notes in Reason to retrigger LFOs in ShaperBox (TimeShaper, FilterShaper Core, VolumeShaper, PanShaper, WidthShaper), FilterShaper 3, MidiShaper and PanCake.

Using this technique, the LFO will play from the beginning each time a MIDI note is received. You can therefore trigger the LFO in any pattern you like – for example, sidechain your bassline to a non-4/4 kick drum pattern.

1. Create a virtual MIDI port

Reason cannot route MIDI directly to VST effects, so you will need to install a virtual MIDI port. This small piece of software lets you route MIDI signals "behind the scenes", like a virtual MIDI cable. We’ll be using it to plug Reason’s MIDI output back into its MIDI input — a technique called "MIDI loopback".


macOS’ built-in IAC driver is all you need for MIDI loopback.

Open the 'Audio MIDI Setup' application – you'll find it in your 'Applications/Utilities' folder, or by doing a Spotlight search (⌘-Space) for "audio midi setup".

In the 'Window' menu, select 'Show MIDI Window', double-click the 'IAC Driver' and make sure 'Device is online' is checked.


On Windows, please install third-party software to provide the virtual MIDI port – for example, LoopMIDI.

2. Enable MIDI Trigger mode

Select a 'MIDI Triggered' or 'MIDI 1-Shot' triggering mode in the Cableguys plugin.

3. Add the EMI device in Reason

In Reason, add an Instruments >> Reason Devices >> External MIDI Instrument (aka EMI) device. Set its output to the virtual MIDI port you set up in Step 1 (e.g., "IAC-driver 1").

4. Insert MIDI notes

On the EMI track, insert MIDI notes in the rhythm that you want to trigger the Cableguys plugin.

Any note will work, except when ShaperBox's MIDI Trigger option for Wave switching is enabled, in which case only C notes will trigger a Wave reset.