Yann: Filters


Oh, excuse me, I didn’t see you there. I was just practicing my filtering.

What’s filtering? Well, funny you should ask! In my very last workshop, at Kilmarnock Academy, Jamie provided a very good example of what a filter sounds like. Give a listen to what he made in the MapMixer:

You see how the bass note seems to be hidden away at the beginning, and then bursts onto the scene 16 seconds in? If you listen carefully, you’ll notice that the pitch of the bass isn’t changing, it’s still the same note but it all of a sudden because much more present. That’s because Jamie was using the filter effect in the MapMixer (the blue one!). Here’s a little explanation of how it works.

The word “filter” is used to describe anything that lets some stuff through, but prevents other things. Just like how a coffee filter lets water through, but not the grounds, providing you with sweet, delicious, wonderful coffee...yum...

Other examples of filters could be fishing nets, colanders, and our mouths.

Yes! It’s true, we use our lips and cheeks to filter sound whenever we talk. That’s what I was doing at the beginning of this blog...try saying “cheeeeoooooooo” - you will almost certainly change the shape of your mouth, but your throat will be making the same sound. Your cheeks and lips, therefore, are filtering some of the frequencies that are coming from your mouth, letting some of them through and preventing others. Some cultures have developed entire musical systems based on this (see Duncan’s page for information about Huun Huur Tu, for example!).

Another common use of audio filters is Equalizers, or EQ. We’ve all seen them on stereo systems, they are the controls labeled “High”, “Mid”, “Low”, or something like that. These controls allow you to independently change the volume of different frequencies (though most people just use them to boost the bass!).

If you’re a guitarist you’ve probably seen or used Wah-Wah pedals. These are filters too - when you rock back and forth on the pedal it is changing which frequencies are being passed from the guitar to the amplifier.

And you too can use the filter in the MapMixer! It’s the blue colored effect. The further to the right you bring the little blue ball, the more high frequencies will be passed through. The higher you bring the ball the more pronounced the filtering will be.

Filters can be used in all sorts of advanced ways, too. One of the more famous things it can be used for is vocoding. I’ll let this very strange video from the 40's film "You'll Find Out" explain how it works!

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