Routing in Reason

With Reason you can make very cool routings. Using the CV (Control Voltage)

With real synths this is a signal wich power depends on the power that is produced by the chosen source. If you choose the filter as the modulator then the signal that is being processed by the filter will set the CV value.
So this is ideal to control parameters on other devices. You can use this to create rhytmic changes in a synthline. Wich are modulated by another synths parameters.
Gate CV is another story. Gate signals are used to trigger things like on/off, velocity, and the starting of lfo's.
When using the Redrum you can see that all channels have a Gate in/out and a Pitch CV in.
These are used to trigger drum sounds and to let their pitch be modulated by a parameter on another device. Such as the lfo/filter of a NN-19, Dr.Rex or a Subtractor.

You could also let one drumsound trigger another. This way you can layer drumsounds very easily in the Redrum. Just connect the gate out of the first sound to the gate in of the second.
Now when playing the first sound the second will also be triggered along with the first one.
The Matrix also has some cool CV functions. The Curve CV out on the back is very usefull to control a parameter on a device. When switching the Matrix from Keys to Curve (On the front) you can draw out a curve and that curve will be controlling the Curve CV output of the Matrix.
The Matrix can be set to Unipolar and Bipolar. Unipolar can be used to control parameters wich use a 0-127 scale. Like: Volume, cutoff, resonance.
Use the bipolar setting to control functions wich have an On or Off seting or for panning. Bipolar gives a middle value and a +/- value.

It's especially fun to use the Curve CV out of the matrix to modulate the pan cv in of a mixer channel. That way you can set panning for the Redrum and Subtractor using patterns or randomly (using an un rhytmic step lenght). You can set the power of the effect by using the turnknob below the Pan CV in of the mixerchannel.

Using These functions can really make your track sound more organic. The results aren't very predictable but if you like your arrangement to have some hidden secrets this is definately the way to go. I use the Matrix a lot. I especially use it to create panning for the Subtractor. It's so easy. Just connect it to the mixerchannel's Pan CV in and draw out a pattern using Bipolar mode. You have enough patterns to make it very interesting.

Just remember that when you save a patch none of the routings you have made will be saved along with it. Neither the routings made on one and the same synth.
But when you save the arrangement it will. So it's a very handy way of giving life to your arrangement. I also like the layering of drum sounds in the Redrum using the gate function. Wanna layer a couple of snares? Just connect the gate out to the gate in and off you go
You can also use a matrix to control a drumsound. Just connect the Matrix Gate CV out to the Gate in of the Redrum channel and the Matrix Note CV out to the Pitch CV in of the Redrum channel.