Is there a guide to using FM in modular?

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daphnid
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Is there a guide to using FM in modular?

Post by daphnid » Fri Jun 19, 2020 7:58 pm

Seems like every VCO and VCF that comes out has one or more FM inputs, and I don't use them for much beyond clangorous percussion sounds. Mainly because I don't know how to patch FM in way that allows me to track pitch in a predictable way (beyond some very subtle linear FM). Is there any kind of guide out there that shows you how to get more extreme/classic FM sounds, like bells and metallic tones, that you can tune to another standard oscillator and get them to both track the same pitch CV? I know that the old Yamahas were using phase modulation and all the operators/carriers could be controlled digitally with musical ratios to one another, making the whole process much easier than trying to dial things in on an continuous knob. But I feel like there's gotta be some way to do this without too much trouble in modular or else every other module wouldn't be throwing all these extra knobs and inputs on the front for FM.

Basically I'm just looking for some tips and tricks. Common ways to apply analog FM musically etc. I just watched the Divkid ZPO review and he's got some amazing tones coming out of that thing. Must learn!

I'm using a Dixie 2+, a Filter 8, and Erica Bassline as my analog oscillators, which all have FM inputs. Thinking of trading in the Bassline for a ZPO or Generate 3 but need to prove to myself I could use it properly first lol.

Also, for the FM pundits, what are your favorite analog VCOs for FM?

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Re: Is there a guide to using FM in modular?

Post by starthief » Fri Jun 19, 2020 10:39 pm

FM is a complex topic. I love it myself, but there's so much to say. (Most of my current oscillators are digital, aside from having Angle Grinder or Ripples self-oscillate. That said, filters that oscillate often make great exponential FM carriers!)

Some tips for exponential FM:
- If you have both the modulator and carrier track the same V/OCT signal, it will generally be less chaotic. That's not to say you can't get some lovely tones by having one of them stay static -- maybe even the carrier.
- The carrier's relative frequency AND the strength of modulation both affect the timbre and the tuning. Don't worry about frequency ratios and don't try to predict the behavior -- just tune frequencies and modulation depth by ear until you find a sweet spot you like. Generally, the more depth you add, the more it will raise the resulting pitch. But...
- ...a useful trick is to run your pitch source through something that can add an offset, before multing it to both oscillators. That way, when you have a timbre you can like, you can retune both oscillators together without mucking up their relationship.
- If you modulate the FM depth, you're going to mess up the tuning. If you use sync to try to fix it, there will be severe consequences on the timbre. That's also likely if you use a PLL to force it to track. With extremely careful offsetting that's related to the FM depth you can maybe compensate, but this is not at all easy. You're better off using wavefolding, distortion, filtering, an LPG etc. for timbral changes with exponential FM.
- Whether digital or analog, every pair of oscillators you use is likely to respond a little differently to FM.
- While most people think of FM as happening with sines, you're really not limited to sines either for the carrier or modulator

For linear FM:
- With linear but non-thru-zero FM, you're not going to get a lot of FM depth without affecting tuning. With many oscillators this is limited for "tuning safety" -- for instance, on Filter 8. With a few (such as the DPO) you can go overboard if you want to.
- Thru-zero FM gives you the ability to push the modulation depth much more, and get Yamaha DX-like sounds. (Yes, the DX did phase modulation, but they are basically the same in character.)

- A good place to start with dynamic FM is to have both oscillators use the same V/OCT source, and tune them to the same frequency (1:1 ratio) or to integer ratios (e.g. if one oscillator is 110 Hz, tune the other to 55, 110, 220, 330, 440, etc.).
- ...however, you can get lots of interesting stuff at other ratios as well. I feel it's generally best to just tune by ear.
- Run the modulator through a VCA before it goes into the FM input, and modulate the depth.
- If you have to, insert a highpass filter (with the cutoff set just barely into the audible range) as the LAST module before the FM input. Not all oscillators have AC coupled linear FM inputs, so if your tuning gets mangled as the depth changes, this could be why.
- One trick for really locking in ratios is to patch from the modulator to the carrier's sync input. Tweak until the nasty buzziness stops and then pull the sync cable (...or leave it, if you like it).
- As with expo FM, you might get away with a fixed modulator frequency if it's high enough.

Phase modulation:
- It's pretty good! More forgiving than "real" FM.
- If you don't have a carrier oscillator that supports phase modulation, you might be able to use a delay. Some delays don't respond readily to audio rate modulation, but some do -- the Disting works very well for this, and Mimeophon does too up to a point. Set the mix to 100% wet, no feedback, and a short delay time. Don't modulate the delay time so much that it hits 0ms or you'll get nasty noise (unless you like the nasty noise).
- Filters affect the phase of the audio that passes through them -- so yes, modulating the cutoff frequency of a filter that has audio running through it, at audio rates, is a form of combined phase modulation and amplitude modulation. The same general rules about frequency ratios apply as to linear FM, but there is no depth limit.
- You can also do "external phase modulation" with a triangle-to-sine shaper or a wavefolder. This is essentially how Happy Nerding FM Aid works.
- If you have an oscillator that's being exponentially FM'd, you cannot also linearly FM it without messing up the tuning. But you CAN phase modulate it without messing up the tuning.

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Re: Is there a guide to using FM in modular?

Post by daphnid » Sat Jun 20, 2020 4:25 am

Wow thanks Starthief, what an amazing reply, thank you. I've been messing with it all night and having better results thanks to some module manuals and your post. I think I'm getting a better grasp on it. Only my Dixie has a sync, and that obviously makes things a lot easier and faster but as you said, limits the timbral range.

I've definitely gotten some interesting results with audiorate modulation of the Filter 8, I'm guessing the delay phase mod trick won't work on the 4MS DLD since it doesn't alter pitch as you move the delay time around.

Trying to avoid buying more modules such as a PLL or FM Aid. They look interesting but I don't really have the space and like to keep my patching relatively simple. The more choices and modules I have to think about, the less music I make, and with the modular I already am overwhelmed with choices so easily. Initially I kind of wanted to have all the odd/west coast sound sculpting utilities I could fit but I quickly realized I just ended up with overly complex patches that weren't very musical (for what I'm doing).

Hopefully I can get a few go-to FM tricks up my sleeve and it'll become somewhat second nature. I just feel like it's something I've been under utilizing because it's frustrating and often unfruitful.

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Re: Is there a guide to using FM in modular?

Post by transistorresistor » Tue Jun 23, 2020 12:35 am

so much good info in there starthief thank you!

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Re: Is there a guide to using FM in modular?

Post by BlinkyLights » Sun Jun 28, 2020 7:32 pm

starthief wrote:
Fri Jun 19, 2020 10:39 pm
FM is a complex topic. I love it myself, but there's so much to say. (Most of my current oscillators are digital, aside from having Angle Grinder or Ripples self-oscillate. That said, filters that oscillate often make great exponential FM carriers!)

Some tips for exponential FM:
- If you have both the modulator and carrier track the same V/OCT signal, it will generally be less chaotic. That's not to say you can't get some lovely tones by having one of them stay static -- maybe even the carrier.
- The carrier's relative frequency AND the strength of modulation both affect the timbre and the tuning. Don't worry about frequency ratios and don't try to predict the behavior -- just tune frequencies and modulation depth by ear until you find a sweet spot you like. Generally, the more depth you add, the more it will raise the resulting pitch. But...
- ...a useful trick is to run your pitch source through something that can add an offset, before multing it to both oscillators. That way, when you have a timbre you can like, you can retune both oscillators together without mucking up their relationship.
- If you modulate the FM depth, you're going to mess up the tuning. If you use sync to try to fix it, there will be severe consequences on the timbre. That's also likely if you use a PLL to force it to track. With extremely careful offsetting that's related to the FM depth you can maybe compensate, but this is not at all easy. You're better off using wavefolding, distortion, filtering, an LPG etc. for timbral changes with exponential FM.
- Whether digital or analog, every pair of oscillators you use is likely to respond a little differently to FM.
- While most people think of FM as happening with sines, you're really not limited to sines either for the carrier or modulator

For linear FM:
- With linear but non-thru-zero FM, you're not going to get a lot of FM depth without affecting tuning. With many oscillators this is limited for "tuning safety" -- for instance, on Filter 8. With a few (such as the DPO) you can go overboard if you want to.
- Thru-zero FM gives you the ability to push the modulation depth much more, and get Yamaha DX-like sounds. (Yes, the DX did phase modulation, but they are basically the same in character.)

- A good place to start with dynamic FM is to have both oscillators use the same V/OCT source, and tune them to the same frequency (1:1 ratio) or to integer ratios (e.g. if one oscillator is 110 Hz, tune the other to 55, 110, 220, 330, 440, etc.).
- ...however, you can get lots of interesting stuff at other ratios as well. I feel it's generally best to just tune by ear.
- Run the modulator through a VCA before it goes into the FM input, and modulate the depth.
- If you have to, insert a highpass filter (with the cutoff set just barely into the audible range) as the LAST module before the FM input. Not all oscillators have AC coupled linear FM inputs, so if your tuning gets mangled as the depth changes, this could be why.
- One trick for really locking in ratios is to patch from the modulator to the carrier's sync input. Tweak until the nasty buzziness stops and then pull the sync cable (...or leave it, if you like it).
- As with expo FM, you might get away with a fixed modulator frequency if it's high enough.

Phase modulation:
- It's pretty good! More forgiving than "real" FM.
- If you don't have a carrier oscillator that supports phase modulation, you might be able to use a delay. Some delays don't respond readily to audio rate modulation, but some do -- the Disting works very well for this, and Mimeophon does too up to a point. Set the mix to 100% wet, no feedback, and a short delay time. Don't modulate the delay time so much that it hits 0ms or you'll get nasty noise (unless you like the nasty noise).
- Filters affect the phase of the audio that passes through them -- so yes, modulating the cutoff frequency of a filter that has audio running through it, at audio rates, is a form of combined phase modulation and amplitude modulation. The same general rules about frequency ratios apply as to linear FM, but there is no depth limit.
- You can also do "external phase modulation" with a triangle-to-sine shaper or a wavefolder. This is essentially how Happy Nerding FM Aid works.
- If you have an oscillator that's being exponentially FM'd, you cannot also linearly FM it without messing up the tuning. But you CAN phase modulate it without messing up the tuning.
Great post. Thanks.

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Re: Is there a guide to using FM in modular?

Post by GuyaGuy » Sun Jun 28, 2020 8:57 pm

Analog FM is definitely one of those underrated forms of synthesis--less so in modular circles though. SSF ZPO is my favorite oscillator for FM. The features are similar to the Generate 3 but the tonal qualities and morphing made it more attractive to me.

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Re: Is there a guide to using FM in modular?

Post by daphnid » Wed Jul 01, 2020 10:26 pm

GuyaGuy wrote:
Sun Jun 28, 2020 8:57 pm
Analog FM is definitely one of those underrated forms of synthesis--less so in modular circles though. SSF ZPO is my favorite oscillator for FM. The features are similar to the Generate 3 but the tonal qualities and morphing made it more attractive to me.
I'll have my ZPO tomorrow, looking forward to exploring it. I had a Rubicon 1 on loan for a while and was unable to get a ton of usable tones out of it beyond the standard analog fare so we'll see. How do you feel about the overall sound of it as a standard oscillator? I've watched a few demos and the tonal range seems pretty insane, but I'm a little worried that it'll sound a bit thin when used as a straightforward VCO. My other analog VCO is a Dixie 2+ and it's pretty clinical and not exactly "full" sounding. Played with a friend's RS Serge NTO the other day and it punched me in the gut.

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Re: Is there a guide to using FM in modular?

Post by GuyaGuy » Thu Jul 02, 2020 11:14 am

daphnid wrote:
Wed Jul 01, 2020 10:26 pm
GuyaGuy wrote:
Sun Jun 28, 2020 8:57 pm
Analog FM is definitely one of those underrated forms of synthesis--less so in modular circles though. SSF ZPO is my favorite oscillator for FM. The features are similar to the Generate 3 but the tonal qualities and morphing made it more attractive to me.
I'll have my ZPO tomorrow, looking forward to exploring it. I had a Rubicon 1 on loan for a while and was unable to get a ton of usable tones out of it beyond the standard analog fare so we'll see. How do you feel about the overall sound of it as a standard oscillator? I've watched a few demos and the tonal range seems pretty insane, but I'm a little worried that it'll sound a bit thin when used as a straightforward VCO. My other analog VCO is a Dixie 2+ and it's pretty clinical and not exactly "full" sounding. Played with a friend's RS Serge NTO the other day and it punched me in the gut.
To be honest I’m not sure I’ve used it much for that—too many options with the wave shaping and so on! The raw waves sound pretty solid; I didn’t notice anything thin about them. But I don’t think I’ve even sent one through a filter. Blending FM outputs and the sub makes for HUGE sounds.

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Re: Is there a guide to using FM in modular?

Post by Pelsea » Thu Jul 02, 2020 12:11 pm

Shameless plug: My book on modular synthesis (follow links in my sig) has 10 pages on modulation, mostly FM.
Books and tutorials on modular synthesis at http://peterelsea.com
Patch responsibly.
pqe

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Re: Is there a guide to using FM in modular?

Post by GuyaGuy » Thu Jul 02, 2020 11:56 pm

daphnid wrote:
Wed Jul 01, 2020 10:26 pm
GuyaGuy wrote:
Sun Jun 28, 2020 8:57 pm
Analog FM is definitely one of those underrated forms of synthesis--less so in modular circles though. SSF ZPO is my favorite oscillator for FM. The features are similar to the Generate 3 but the tonal qualities and morphing made it more attractive to me.
I'll have my ZPO tomorrow, looking forward to exploring it. I had a Rubicon 1 on loan for a while and was unable to get a ton of usable tones out of it beyond the standard analog fare so we'll see. How do you feel about the overall sound of it as a standard oscillator? I've watched a few demos and the tonal range seems pretty insane, but I'm a little worried that it'll sound a bit thin when used as a straightforward VCO. My other analog VCO is a Dixie 2+ and it's pretty clinical and not exactly "full" sounding. Played with a friend's RS Serge NTO the other day and it punched me in the gut.
Spent some time tonight sending the ZPO into my Pro 3. Those standard shapes can more than hang with the Pro 3's VCOs! But sending some of the more complex shapes into the filter is quite delightful!

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Re: Is there a guide to using FM in modular?

Post by daphnid » Fri Jul 03, 2020 1:07 am

GuyaGuy wrote:
Thu Jul 02, 2020 11:56 pm
Spent some time tonight sending the ZPO into my Pro 3. Those standard shapes can more than hang with the Pro 3's VCOs! But sending some of the more complex shapes into the filter is quite delightful!
Ah word! I got mine this morning and have spent about 5 hours with it. Honestly couldn't be happier. It sounds great just straight into a filter (tried with a VCF-74 and Addac702) and paired up with a slightly detuned Dixie. Spent most of the time though doing insane audiorate modulation stuff and man it's just much easier to get useful FM sounds out of it than my other oscillators.

I have it lined up next to the Dixie and an E352 and cross patching them all together makes for an absolutely bonkers complex VCO. :bop:

I think I'm well satisfied with my VCO lineup now and am finally making headway into modular FM. Again, thanks for your post Starthief, and for anyone else looking for some FM guidance, I found some good stuff in the Rubicon manual.

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Re: Is there a guide to using FM in modular?

Post by ignatius » Fri Jul 03, 2020 1:11 am

this old thread has lot's of tid bits about FM with analog oscillators.

viewtopic.php?f=16&t=11481

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Re: Is there a guide to using FM in modular?

Post by frijitz » Fri Jul 31, 2020 6:52 pm

I have demonstrated that a touch of soft sync between master and slave can give good tracking with minimal timbral shifts. See the original thread on the Threeler on e-mus. Spectra and sonograms of wide-range audio sweeps are presented.

Ian

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Re: Is there a guide to using FM in modular?

Post by DrReverendSeance » Fri Jul 31, 2020 7:28 pm

Pelsea wrote:
Thu Jul 02, 2020 12:11 pm
Shameless plug: My book on modular synthesis (follow links in my sig) has 10 pages on modulation, mostly FM.
I’m reading Pelsea’s book right now - it is very well written, concise manual. Well done! And the section on FM is very clear.

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Re: Is there a guide to using FM in modular?

Post by EATyourGUITAR » Sat Aug 01, 2020 12:28 am

Dr John Chowning is the FM guy. This video will amaze you. he has many published scientific papers on the subject.
WWW.EATYOURGUITAR.COM <---- MY DIY STUFF

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Re: Is there a guide to using FM in modular?

Post by Bachelard » Sun Aug 02, 2020 11:08 am

I've asked this question to my local modular group with a LOT of very technical and knowledgeable people and can actually explain FM on a technical level, but I think in a practical context, in making sounds that inspires you to create musical pieces, use your ears.

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Re: Is there a guide to using FM in modular?

Post by BlinkyLights » Wed Jan 13, 2021 5:49 pm

EATyourGUITAR wrote:
Sat Aug 01, 2020 12:28 am
Dr John Chowning is the FM guy. This video will amaze you. he has many published scientific papers on the subject.
Fantastic video.

What a legend.

Thanks.

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Re: Is there a guide to using FM in modular?

Post by grizzleb » Wed Jan 13, 2021 6:07 pm

starthief wrote:
Fri Jun 19, 2020 10:39 pm
FM is a complex topic. I love it myself, but there's so much to say. (Most of my current oscillators are digital, aside from having Angle Grinder or Ripples self-oscillate. That said, filters that oscillate often make great exponential FM carriers!)

Some tips for exponential FM:
- If you have both the modulator and carrier track the same V/OCT signal, it will generally be less chaotic. That's not to say you can't get some lovely tones by having one of them stay static -- maybe even the carrier.
- The carrier's relative frequency AND the strength of modulation both affect the timbre and the tuning. Don't worry about frequency ratios and don't try to predict the behavior -- just tune frequencies and modulation depth by ear until you find a sweet spot you like. Generally, the more depth you add, the more it will raise the resulting pitch. But...
- ...a useful trick is to run your pitch source through something that can add an offset, before multing it to both oscillators. That way, when you have a timbre you can like, you can retune both oscillators together without mucking up their relationship.
- If you modulate the FM depth, you're going to mess up the tuning. If you use sync to try to fix it, there will be severe consequences on the timbre. That's also likely if you use a PLL to force it to track. With extremely careful offsetting that's related to the FM depth you can maybe compensate, but this is not at all easy. You're better off using wavefolding, distortion, filtering, an LPG etc. for timbral changes with exponential FM.
- Whether digital or analog, every pair of oscillators you use is likely to respond a little differently to FM.
- While most people think of FM as happening with sines, you're really not limited to sines either for the carrier or modulator

For linear FM:
- With linear but non-thru-zero FM, you're not going to get a lot of FM depth without affecting tuning. With many oscillators this is limited for "tuning safety" -- for instance, on Filter 8. With a few (such as the DPO) you can go overboard if you want to.
- Thru-zero FM gives you the ability to push the modulation depth much more, and get Yamaha DX-like sounds. (Yes, the DX did phase modulation, but they are basically the same in character.)

- A good place to start with dynamic FM is to have both oscillators use the same V/OCT source, and tune them to the same frequency (1:1 ratio) or to integer ratios (e.g. if one oscillator is 110 Hz, tune the other to 55, 110, 220, 330, 440, etc.).
- ...however, you can get lots of interesting stuff at other ratios as well. I feel it's generally best to just tune by ear.
- Run the modulator through a VCA before it goes into the FM input, and modulate the depth.
- If you have to, insert a highpass filter (with the cutoff set just barely into the audible range) as the LAST module before the FM input. Not all oscillators have AC coupled linear FM inputs, so if your tuning gets mangled as the depth changes, this could be why.
- One trick for really locking in ratios is to patch from the modulator to the carrier's sync input. Tweak until the nasty buzziness stops and then pull the sync cable (...or leave it, if you like it).
- As with expo FM, you might get away with a fixed modulator frequency if it's high enough.

Phase modulation:
- It's pretty good! More forgiving than "real" FM.
- If you don't have a carrier oscillator that supports phase modulation, you might be able to use a delay. Some delays don't respond readily to audio rate modulation, but some do -- the Disting works very well for this, and Mimeophon does too up to a point. Set the mix to 100% wet, no feedback, and a short delay time. Don't modulate the delay time so much that it hits 0ms or you'll get nasty noise (unless you like the nasty noise).
- Filters affect the phase of the audio that passes through them -- so yes, modulating the cutoff frequency of a filter that has audio running through it, at audio rates, is a form of combined phase modulation and amplitude modulation. The same general rules about frequency ratios apply as to linear FM, but there is no depth limit.
- You can also do "external phase modulation" with a triangle-to-sine shaper or a wavefolder. This is essentially how Happy Nerding FM Aid works.
- If you have an oscillator that's being exponentially FM'd, you cannot also linearly FM it without messing up the tuning. But you CAN phase modulate it without messing up the tuning.
Thanks for this post! Bookmarking this thread for when I got some spare time to really dig into this a little... Thanks! :sb:

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Re: Is there a guide to using FM in modular?

Post by Countcowden » Wed Jan 13, 2021 7:55 pm



I found this video quite useful

Going to check Dr Chowning later

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