Ed.: Feedback loops usually fall into the “things to avoid” category, but cleverly used, they can be a powerful creative technique. Part of what Kore is about is being able to create unusual routings easily, so where better to start than a loop? Eoin walks us through sound design with feedback here, using an external input (like a mic) or plug-in as a source, or even self-oscillating (crank up the gain, and the setup itself will produce its own sound). -PK
If you’ve read the Kore 2 manual, you might have seen mention of the possibility of feedback loops, but there are no instructions for how to safely set this up. Today we’re going to do this step by step, and hopefully by the end you’ll have an idea of how easy this is and the kind of wild sounds you can get.
If you don’t have access to Kore, you can still hear the end results; the audio examples below demonstrate some of the sounds that can be obtained with just a few simple routings.
You can use the Kore demo to complete tutorials; sessions shut down every 30 minutes, and saving is disabled, but there are no other limitations. The examples included work with Kore 2′s internal engines and effects.
Before We Begin
While you definitely don’t need a hardware Kore controller to do any of this, it will make adjusting assigned values much easier. We’ve included instructions on which knobs to assign and when. Before we begin, you should know that creating signal routings of this type can seriously damage your ears and speakers. Monitor at low volumes and put a limiter on your Master channel (there is one in Kore’s included effects). Now, let’s use feedback as a force for good!
1. Create the sound. Open up Kore and create a Source channel if there’s not an empty one already. Right-click in a sound slot here and click New Sound. This will be our ‘container’ for the entire feedback loop, which we can then save as a .ksd (KoreSound file).
2. Add a Limiter. Put a Limiter device on the container sound’s Master channel (you’ll find this in Kore’s Internal Effects menu). Leave the controls at 12:00 and decrease the Out Gain to -3dB.
3. Make a “kill” knob and button. Assign your top left-hand knob to the Sound’s Master Volume control (to the far right of the controller area) — this gives you quick access to the master level. Assign a button to bypass the sound altogether by first clicking on Learn and then on either the sound’s channel number or the little circle icon next to the sound’s name. Between these and the Limiter, you’ve got plenty of ‘insurance’ in case you need to lower the volume in a hurry.
Create an Input Channel
Mic input: If you’re using a mic, right-click a sound slot in your container sound and select New Sound. Create an Input channel and assign a knob to the Input Gain control (and a button to mute the incoming sound if you like). Using the Input Source selector, route an audio signal into this channel. Place a Mic Conditioner device on the Input channel and turn on the MS to LR button (pictured). This will convert mono mic signals to stereo. You can also filter low frequencies with the Mic Conditioner and introduce a little delay on either channel to thicken up the sound.
Plug-in input: If you want to use a plug-in as a sound source, right-click a sound slot in your container sound and select New Sound. Create a Source channel, name it ‘Input’ and simply insert whichever plug-in you want to use.
Create Feedback Channels
A Rotor for effect: Next, create a Group Channel beside your input channel, put a Rotor device in it and call it ‘Rotor’ for clarity. You don’t necessarily have to have any effects here, but this one allows you to vary the dynamics in interesting ways and add some grit. Lower the Input gain on this channel to about -4dB, and assign a knob to the Output level. As we’ll want a more subtle control over the feedback amount, we’re going to limit the Output level to between -13dB and -8dB. To do this, click on the Assign Tab for your Rotor Output level knob and limit the Min and Max values for the assignment to 47 and 56, respectively. Call this knob ‘Feedback’ [Fbk].
In the Rotor device adjust the settings as shown in the screenshot and assign a knob to the Fast knob. Feel free to assign other controls you think might be fun to play around with – High Cut, Low Cut and the Fast button are all good contenders.
Delay the loop: Next create a Group Bus, call it Delay and put in another Mic Conditioner device. Add some delay time. Somewhere between 100 and 200ms on both channels is fine; it’s not an exact science & doesn’t matter if the two channels are different. This ‘buffer’ will prevent our feedback loop from getting out of control too quickly. Again, you can assign macro knobs to parameters here, but remember, the lower the delay setting, the easier it will be to send your feedback loop straight into overdrive.
This Rotary Speaker channel and Delay channel together will be our feedback loop. Let’s connect them and see what it sounds like.
Make your routings
Change the output routing of your Input channel from Master to Rotor. On your Rotor Channel, change the Output routing from Master to Delay (your Output Level assignment will stay in place with its limits intact).
Complete the feedback loop
Now on the Delay channel, assign your first aux send to Rotor. Make some noise in the mic (or your sound source) and you should be able to set the sound feeding back onto itself. If not, check your input gain and the feedback amount. A cool trick to try is to just let the sound self-oscillate. Simply turn the feedback knob up full and wait a while… even with no sound source you can get a working feedback loop in this way.
You’ll notice it can be tricky to keep the signal feeding back at the same level. It takes a bit of a balancing act to get it right, but you should be able to get a stable loop to work with. If the level meters within the Rotor/Delay channels are fully in the red, don’t worry about it – this digital distortion provides a tasty crunch that’s high in fibre
Once the sound is feeding back and not rising or falling in volume, its timbre pretty much stays the same. This is where the fun starts – by making tiny variations in seemingly unimportant FX parameters, you can completely alter the sound of the loop. If you hit on the right combination, the sound can start to take on a life of its own… try minutely altering the Delay settings or adjusting the Mix control on the Rotor device.
After this, you can basically add effects to taste. As an example, I’ve created a KoreSound that contains a feedback loop and some of Kore 2′s Internal Effects. In this case, the feedback loop doesn’t go directly to the Master, but passes through the effects first. I’ve recorded some example MP3s of improvisations with the .ksd to give you a feel for what can be achieved if you want to delve further.
Ed.: You might want to turn down your volume to avoid upsetting neighbors / cats / small children — Doctor Who fans, enjoy!
KoreSound .ksd file
You can insert other effects to either channel directly within the feedback loop if you like (watch your levels), but the more devices you add to the chain, the more difficult it’ll be to diagnose problems if it’s not behaving the way you expect. It might be a good idea to have each plug-in change the sound in only one way, such as just impacting dynamics or just changing the pitch, so that you can better predict what will happen if you disable it.
When you’re finished following through the article, don’t forget to come back and show us your own variations on this theme!