Circle Tutorial 4 - Creating a Noise Based Sweep Effect

What is Covered?
An intermediate level tutorial on creating a noise based sweep effect.
Introduces the design of sound effects and how to use the filter and noise source.


So far we have looked at how to go about creating some basic instrument patches using Circle, now lets focus on building some classic synth sound fx.

Some synth fx based patches are surprisingly easy to program and can be really effective in the mix. Of course there are plenty of samples around that recreate these sounds but the control you gain when creating your own is second to none and of course you'll have the satisfaction of knowing its 100% original.

Step 1 - It's just noise

Circle has already been initialised by hitting the 'new' button at the top of Circles interface and is now ready for programming.

The initialised patch

For this effect we are simply using one noise oscillator, so the initial saw wave oscillator is turned off and replaced by the dedicated noise oscillator further down the interface. The noise oscillator is very basic and only has a few options. Here we have opted for the low pass filter version, fully open. This gives us the most harmonically rich noise source available in Circle.

The noise oscillator

The noise oscillator

The single noise oscillator

Step 2 - A very resonant filter

To achieve the desired effect here we will need to use a resonant low pass filter with a pretty high resonance setting. We don't want the filter to 'self oscillate' but we are trying to add as much harmonic content to the sound as possible. To demonstrate the amount of resonance I have added here a manual sweep was recorded.

Filter setting

The combination of the noise based sound source and the aggressive filter settings really just give us an excellent blank canvas. With this sound we can add numerous modulations to create any number of exciting effects patches.

Filter with high resonance setting

Step 3 - Initial modulations

Creating an fx based patch like this is really all about the modulation. The only real limit here is your imagination and the amount of free mod slots available! But to make things really interesting a few different modulators need to be activated so let's look at the first few.

We are after a falling, laser like sound here so the first thing to achieve is a downward sweep of the filter cut off frequency. To do this we'll use an envelope as a modulator and we'll also set the amplitude envelope at the same time.

The new envelope settings

You can see that by using a long decay time combined with a low sustain setting and long release, we get the downward sweep we are after. I have pretty much zeroed the amplitude filter, apart from some release that matches that of the filter envelope.

Once the settings were correct I adjusted the filter cut off so that the sweep took place from exactly the right point. The final result is a nice even sweep across the whole frequency range. This is the basis of our effect and now its simply a case of routing more modulations and adding some final touches.

The filter is adjusted

The filter sweep

Step 4 - Modulating the filter with an LFO.

As the filter falls I wanted to create a wobble that fades in and also changes in speed. Circles LFOs are really flexible and just about anything is possible, so this task proved to be pretty easy.

I simply set up a standard sine wave based LFO, dialled in some fade and delay so that the initial part of the effect remained untouched and then the speed is modulated by the same envelope that is controlling the filter. Using the same envelope not only saves modulation slots but ensures the drop in speed gels with the rest of the sound.

Filter LFO

It was then just a case of moving back over to the filter and balancing the cut off and modulation amounts so everything worked together nicely.

Final filter settings

LFO modulated filter

Step 5 - Adding some modulated effects

Our sound is now pretty much finished but to add some extra movement and sparkle to the end result, lets look at how to use modulation with Circle's built in multi fx processor.

The panner effect is always useful to create some movement in the stereo field but un-modulated it is simply a pan knob that remains static once set. In this case i simply attached it to a new LFO with a relatively slow rate setting. This immediately creates an auto panner effect and really adds interest to our patch. Remember that if you are using Circle within a DAW that the LFOs can be synced to your hosts bpm.

LFO creating an auto panning effect

The second effect I used was a simple hall reverb but the twist is that the mix parameter is controlled by the filter envelope. A negative value has been dialled in here so that the level of the reverb increases as the level of the envelope decreases. This results in the reverb effect becoming more intense towards the end of the sounds cycle.

This is a really effective sound to use in the mix and is pretty simple to construct. Next we'll look at other synth effects that can be created using Circle that are also suitable for the relative beginner.

Modulated Panner and Reverb effects

Final patch with effects

Download Tutorial 4 Files

Tutorial 4: Creating a Noise Based Sweep Effect
Download the tutorial in plain text format, the associated audio files and the completed Circle sound/patch.