A Comb filter adds a delayed version of the signal to itself with adjustable feedback (controlled by the Peak knob in the Pulveriser). It’s a rather basic form of filtering but the results can be very dramatic. Reason’s Pulveriser has a Filter section which has a wide range for creating these Comb filter effects. Set the Frequency of the Filter to its lowest setting and you’ll hear clearly that this filter is using a delay.

Comb filters are often used in electronic music because of its metallic sounds and artificial impact they have on sound. What I want to show you today is how you can use the Pulveriser for these kind of Comb effect while playing the effect live, as a performance.

How to play an effect?

We have many options to control a filter in a performance. Most often we will be using the modulation wheel on a keyboard or one of the pots on our controller. That works great for sweeps but doesn’t always work for very precise switching because certain values. This is exactly what I want to do. So therefore I decided to use the keys of my keyboard for this. Instead of using the mod wheel I want to use my keys to send out a precise level of CV to the CV Modulation Input of Filter Frequency on the Pulveriser. This way I can play the effect by using a keyboard (or type in the notes on the sequencer if I don’t want to perform).

We need Thor!

If you’re wondering what device can output the note value as CV: Thor can do that. Just create a Thor and reset it. We don’t need any oscillators or filters in Thor we only need the modulation panel for setting up MIDI Note as source (amount: 100) and make CV Out1 output that as a CV value. It should look like this:

Now when we play Thor it creates a unique CV output (CV 1 which can be found at the Modulation Output on the back of Thor) for every note.

We need to add a Spider CV for making the CV value twice as high for better results. Like I have shown in the post ‘Finger on the Trigger’. We can send that Spider CV merge output to the Filter Frequency CV input on the back of the Pulveriser and start playing the effect by using a keyboard.

It’s best to create a Combinator with these 3 devices so you can save the configuration and maybe to add a few more live controls. I made a short demo song for this config, please listen: