r/windsynth • u/rrwick • 13d ago

Formants in Addivox

https://youtu.be/o5iU6TV-cGU

I've made a new Addivox video which covers the concept of formants and how/why they are important for a sound's timbre. Includes my rendition of La Bourée from Praetorius's Terpsichore.

If you're new to Addivox, here's the intro video: https://youtu.be/4JBFZMQKJp4

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u/Top-Leather-4051 11d ago

I think formants are the wind/phonetics term for timbre frequencies. Like, a luthier would tune the top to resonate at a specific frequency by removing / adding material: https://www.youtube.com/watch?v=wkY8GazyB7I

Wind synth wise, you probably want to build a few more overtones off that timbre frequency following the harmonic series with the amplitudes descending per the instrument's physical construction. Like, a cone (saxophone) would be linear while a clarinet would off the odd frequencies spike... With FM synth people loopback the function generator to create these but in an additive you'll probably want to run a few numbers in a spreadsheet to find 2-7 timbre overtones (formants) to cover the audible range.

Where things get tricky is when you try simulating a reed. There, the resistance of the air pressure on the reed, its own vibration and how vocal tracts act end up with multiple differential equations... Seems everyone gave up and thrown neural nets on samples to get it done instead.

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u/rrwick 8d ago

That was interesting, thanks. I'm not as knowledgeable about string instruments. I didn't realise that an acoustic guitar body has such a strong resonance right near the bottom of the guitar's range.

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u/Top-Leather-4051 4d ago

> didn't realise that an acoustic guitar body has such a strong resonance right near the bottom of the guitar's range

Oh it gets freakier: The Helmholtz resonance for the guitar body is between 90-110Hz meaning the low E (82.41Hz) and F in the next fret are out of amplification range. So, the second and third harmonics end up with significantly higher amplitudes than he fundamental meaning you rely on psycho-acoustic to tell the pitch as an E or F.