Understanding FM #4 - Virtual tones and how sidebands become harmonics

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If this is the first of my videos on FM you're seeing, you might want to pop back to the start of the playlist, as a lot of what I talk about this week relies on it: • Understanding Frequenc...
Did you know that the ratio between carrier & modulator frequencies can define a sort of "virtual tone" at a lower frequency? And that ratio will tell you how complete the harmonic series for that new tone is? Well, at the end of this video you certainly will!
Actually, this is a video I struggled with a bit. I think it is really interesting, and has something to say about what FM does, and how sound works in general. I'm also not 100% sure that it's really useful to people when it comes to actually using FM synthesis.
But my goal here was to explain what FM was really doing, so here you go.
During this video I show an abbreviated version of a demo, if you want to see the whole thing, you can check it out on my second channel, ‪@SoundsofVoltage‬

Опубликовано:

12 сен 2024

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Комментарии : 26

@Pro-gressive 21 день назад

"You probably don't want to see whole five minutes..." Yes I do! "It's posted on the second channel" Thanks!!!! Edit: the video comparing ratios sounds very cool also.

@moa643 20 дней назад

This series is awesome, makes learning FM engaging and interesting. I’m really looking forward to the patching episode, my Reface DX is begging for a competent “operator” lol.

@GeorgeLocke 20 дней назад

Oscillator Sink had a good tip to help predict the effect of modulation ratio. When the ratio is closer to one, the effect feels like shaping the fundamental. When the ratio is much bigger than one, it sounds like adding high ringing harmonics. Simple.

@SvenRonPooc11 20 дней назад

This is really interesting. Looking forward to the next part in the series

@Probbie 21 день назад

Fascinating, and very well presented 😊

@SoundVoltage 21 день назад

Thank you so much!

@GillamtheGreatest 21 день назад

loving the series so far

@SoundVoltage 21 день назад

I'm glad you're enjoying it!

@dillipphunbar7924 21 день назад

I tried with Brains fm algo (modulator) into 2600-VCO (carrier) but struggled as I was making it overcomplicated by sending a 2-OP (already) FM mod in which made it almost impossible to get a stable result. Don't have a Mordax, but the Korg NTS-2 is really useful. It does my head in, but I do love that FM sound. I blame the 80's. Still enjoying these explorative videos. Please continue.

@GeorgeLocke 20 дней назад

The 2600 VCO doesn't have linear FM so the whole discussion here won't apply. Exponential FM will mess with perceived pitch even with sine waves.

@CyberBlob69 20 дней назад

Great series, having fun following it with some Matlab implementation.

@SoundVoltage 20 дней назад

@CyberBlob69 - That's excellent! There's a good mathy episode coming up next!

@michaeltristan 17 дней назад

serious meditative qualities in this video. similar vibes to those alan watts videos..

@plop-4269 21 день назад

Nice !

@PinkKittenTech 19 дней назад

This is fantastic, it's like 3blue1brown but specific to music.

@SoundVoltage 19 дней назад

@PinkKittenTech - Thanks so much! It's probably pretty clear that 3b1b is one of my big influences. Just wait for the next video, it's all mathy. :)

@kenaestheticfm 21 день назад

Great series.

@SoundVoltage 21 день назад

Thanks!

@hoperanker8395 21 день назад

Loving this video series. Thanks so much! If you ever get the chance, I'd especially love to build my intuitions for how FM works in an exponential system like eurorack's volt per octave. So like, if I tune my carrier and modulator to the same base pitch and then start feeding them piches from the same sequencer, what happens? What if I always add 1V (1 octave) to the pitch that goes into of them? What about adding a perfect fifth? What if the base piches aren't in tune; say I tune the modulator to a fifth above the carrier, and then feed them from the same sequencer again? Obviously I can built some of these intuotions by ear, but I'd love to see the math worked out the way you're doing it here. Anyway, irrespective of whether that ever fits into your series, I'm lobing it, and I'm already looking forward to the next one. Thanks!!

@SoundVoltage 21 день назад

@hoperanker8395 - I'll be digging into this more in an upcoming patching video (probably the one after the next one), but feeding the sequencer into both the carrier and modulator is really important if you want to be able to 'play' the result in a consistent way. For instance, imagine you have a 440 hz carrier and 220 hz modulator, so it's a 2:1 relationship. Now add 1V pitch CV to each. 440 hz goes up by an octave to 880 hz. And 220 hz goes up an octave to 440 hz. That is still a 2:1 ratio - so the effect that the modulation has will be the same, just pitched up. Same goes for a fifth. Say the carrier is at 220 hz, a fifth above that would be 330 hz, so it's a ratio of 2:3. Now add 1V to each. 220 goes up an octave to 440, and 330 goes up to 660, but the ratio is still 2:3. Glad you're enjoying the videos!

@Overcrox 21 день назад

An idea that popped into my head (and forgive me if you've already covered this and I forgot!) which may or may not have any merit due to how sidebands appear on *both* sides of the carrier, is whether you could do "virtual chords" by using specific ratios in combination with specific notes for the carrier to use the virtual pitch of the audio-rate modulation as a second/third note, sort of "tuning" the modulation to fit into the composition. I haven't tried it yet and I have no idea if it could work, and maybe someone's already thought of this, but I'm very intrigued by the idea.

@oksami 21 день назад

very nice

@SoundVoltage 21 день назад

Thanks!

@chinossynthesizer705 9 дней назад

I have a Kodamo essence fm mk2. I programmed amazing fm sounds, but somethings missing i need more variety of timbres instead of carriers multiplied 1 and modulator by 1. I can also make custom wavforms as well for carriers and modulators.

@vojkofau 20 дней назад

i thought the sidebands under 0 and over half the sample rate appear "mirrored" only in the digital world(aliasing) and I see you are using analog gear🤔

@tezeta3725 12 дней назад

I think you're conflating two different things. Aliasing only happens with frequencies that go over Nyquist afaik. It's the result of not having enough sample data to accurately represent a wave. I think I missed the last episode so I don't know the exact mechanics of the sidebands reflecting from 0, but it's definitely a different phenomenon from aliasing.