Automate Anything
The Reason sequencer allows for nearly any parameter to be automated. This can be performed through an input device, MIDI controller, or drawn in by hand. I like to perform certain actions to see the relative timings and types of input motion which come from nudging, flicking, and sliding faders that add a layer of performative modulation. There is a truth to this type of input which says "a person made this", but that is not to say that automatic, repetitive input modulations don't have their place in creating music, but I like the sense of some organic influence that can be apparent when things are not perfectly sterile and mechanistic.
There is this oft overlooked feature of the Reason sequencer (circled in red) which is quietly waiting for you to discover all of the amazing things you can quickly and easily automate. Select an instrument, VST, or effect in the Sequencer view and click it to see what's possible.
Here we can see three channels of automation that I added to modulate the performance of a French Horn part. In this case I have used a Combinator to contain an instance of Audio Modelling's Swam Horn and have mapped three controllers to the Expression, Mute and Growl parameters of the horn part. This enables a much more lifelike sound to be produced.