In this article I will explain how to record your Control Voltage outputs on an automation lane. It may require some external tools to make it work. While I am not familiar with Apple / Macs I am mainly focusing on how it works on windows (you may need only one specific tool (as it was mentioned in an article about VST in Reason, a Mac user confirmed that soundflower does the trick).
The source control voltage can be anything. It could be an Low Frequency Oscillator (LFO) are it could be looping envelope. The idea is to throw the CV output against the Loop midi device and thus it will send it back to a different device which is the receiving end (thus records the automation on the sequencer).
To make it all work you will need an external program as a midi loop. For windows this would be Loopmidi for Mac this would be soundflower. From this point on I'll mainly talk about Loopmidi (because I am not a Mac user).
After launching loopMidi you can add different ports with a specific name.
For this one I will create one port which is in this case called "loopMidi Port 1". The loopMidi Port 1 will later on be used as a 'sender' and a 'receiver' for two different instruments at the same time.
Sending out Midi using the External Midi device
The trick I will be applying in this context works since Reason 7 and above. I know there are different ways to make the same logic work using Rewire (but that is a whole different setup). The external Midi device needs to be connected to our created 'virtual' midi port. For the next step we'll be creating an instance of External Midi Instrument. Make sure that the loopMidi Port matches with the one from the program of loopMidi (or soundflower if you use that).
In this case the external Midi instrument is set to loopMidi Port 1. Which matches with the same of the loopmidi program.
Next up we can decide to use a combinator to route cv, or we could route CV directly in to the midi device itself. Like this:
In this case I will be using the LFO2 as a CV Output. At the same time I could have been using the LFO 2 output directly. But in this case the source can basically be anything (mod envelope / filter envelope / oscillator etc).
If you assign it to a CC Port, you'll need to know which CC port is doing what.
In this case I will be using the Modwheel controller. which stands for CC-1. Alternative route would be using the Modwheel CV input / Pitch wheel CV input. In case you will be assigning a specific CC port make sure you'll enable the program and CC buttons that go with it.
From this point the Control Voltage sender should be working. You can fact check the "throughput" if it actually receives any data.
Setting up the Control Voltage Receiver
To make the receiver work, we need to implement the midi device in reason itself. You will need to go to the Edit > Preferences > Control Surfaces section. In this section you can add a Generic Midi keyboard, where the midi input needs to be set to the same loopMidi port we have been creating from the start. In this case this would be loopMidi Port 1.
When hitting Ok, the control surface should be marked as 'Ok'. If this is not the case recheck the port your using.
From this point on, any device you will be attaching will be receiving the loopMidi signals. In case you have selected the Midi Instrument itself, it will record the CV on that instrument as well. So the only thing you'll need is attach an instrument. Right click on Edit Automation on the modwheel (since I am using CC1 in this case it will be the same as the modwheel) and hit record.
And this is how you can record CV outputs using Reason.
A video about this setup
In case this is too much text, here is a video I recorded that explains the exact same thing.
Written by hydlide