The Beauty and the Mystery: Feedback Loops
By Donald Dinsmore
What is feedback and how can it be used in sound design? Feedback as we know it, is a special kind of positive feedback loop where a sound loop is created between a sound input and a sound output. The classic example is the horrifying and ear piercing screech of a microphone getting too close to a loudspeaker. In this case, the signal received by the microphone is amplified and passed out of the loudspeaker. The sound from the loudspeaker can then be received by the microphone, amplified and passed out the loudspeaker again and again and again creating a feedback loop.
The screech of feedback is not often thought of as musical but that hasn't stopped some of the worlds greatest musicians from using feedback in their songs. The first example of feedback being used in a chart topping track was in the introduction of The Beatles 1964 hit, "I Feel Fine." Guitar players around that time were starting to realize that the holding their guitar pickups near their amplifiers resulted in feedback and the pitch of that feedback was determined by the distance and angle of the guitar was held with respect to the amplifier. This breakthrough allowed guitar players to match the pitch of the feedback to the key of the song. Another iconic example of feedback was the performance of Wild Thing by Jimi Hendrix at Monterey Pop Festival in 1967. I can't find a Youtube video of this for copyright reasons so be satisfied with this clip of Jimi sacrificing his guitar at Monterey Pop Festival shortly after his performance of Wild Thing.
Lucky you can recreate the complex, dynamic and magical feedback based sounds in a modern DAW like Ableton using Sends and Returns. I think this trick is most useful for making evolving soundscapes but feel free to use it any way you would like. Here it is:
Here are a couple suggestions/warnings to get you off on the right foot. Use a limiter on the Return Track. This way at you won't clip the signal. Use odd combinations of effects on your return tracks. Use Delays, Reverbs, Chorus, Distortion, Bit Crushers, you get the idea. Anything is fair game and you don't know what you might create until you make it. To add movement automate certain parameters on the Audio Effects. Bounce down the output of the return track to audio by exporting it as a wav file or using the Resample function from the I/O section of Ableton.
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