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FM Synthesis Basics

The very first topic that we cover today is fm synthesis, which is among the more complicated things like out of this that this is was kind of a kind of a big deal it is a bit of a sort of a new a new kind of very modern way of doing things but fm is something that's just always been very confusing and very unique so that's what we're doing that with today and so the first thing that we're going toe we're going to mention is just the comparison between um, how it works and the real world this is how it works in the digital world because there it's it's very different it doesn't matter when it comes to sort of what uh what sounds and you want to make it and how you go about making them with the idea of what we're forms do what have they all work when I kind of think, uh after that but more toss yeah, phase modulation is actually how are you doing that? We'll talk about that and everything routings how oscillators like how you most most fm synthesizers have this matrix fee, which we'll s...

ee what we as you can see it right now in the picture of such us that we're using f inmate has a similar thing toxic biohazard, which is another image line fm since no kind of had this matrix view and the routing it was pretty simple is like any kind of rounding that works. One of them is gonna work on, uh, the arrests really was always a little bit of family and the the most basic concepts. Davey idea that volume controls like the f l amounts you want change the amount of that family changed the volume of the bunch, a leading operator, which I'm acting as if it's some kind of revelation, because for me it was for years and years and just had at just viewed fm is a magical sort of special modulation type push. I mean, it is but it's still grounded in basic ideas of being like it is not. Slater has a level and you change the level, and it also it's less amplitude. That kind of idea just blew my mind apart, recording his next that's part two today. Yeah, segment two of day to so many two's prostitute's son was goingto get right in talking about what we got here. Uh, actually, the thing that I already did, we're not going to go because we're gonna start from scratch. So amusing said just showed us off because it's it's, my personal fm, sent the choice. I know that information more popular but just assed faras core fm I said most of them are the same, but it's so that the differences between the fm insists that we have available muslim is what they let you do with it you know my personal opinion centrist lets you do more let's talk about what I have actually is f m the two letters stands for frequency modulation as we covered on the previous day the idea frequency is pitch how fast the oscillations will be safer modulating that we're changing how that basically the pitch of a way form by another way for him and we also discussed the idea of what a lfo is versus a regular us later and that in the real world everything is just oscillators and what telephone is versus what audio right off later is it's just that one a slower than the other considerably um but like the real world we're able to kind of it's about taking announce later like if I were having a sign wave here to play laura one side waving unify modulated I imagine it's pitch by never sign with we get a sign that you're probably familiar with if you've ever just opened up enough time since on modulated assigned way by no sight away it's just very kind of basic sound but this is happening this the side wave is modulating those I wave as fast as just it's pitches which is somewhere in the eighty hurts range so it's moving the pitch up and down eighty times a sec which is even a base level it's, very fast, but even even play higher and higher notes. We're getting into the hundreds of hurts and even all the way up with high, I don't get the blood going to keep doing it, uh, well, let's, look at what actually what's what's really doing by playing, making the oscillator modulating eyes that are very slow so that we're looking at just a open down, up and down so much. Not much going on there. That's pretty much that's, really all that. I was doing just a lot faster raylan mouse pad space. So that should that you kind of give you a cool like much, a much more like a sort of logical look at what fm is in terms of the process because it is a little bit. It is happening so fast that it's hard to discern sort of its movement, which is the whole point. The idea that you modulated something at audio rate, which is you cannot discern individual motion. It becomes a tone, but because it's happening so fast certain characteristics were not immediately clear like I mentioned it's eddie, that you can make a model and something by on your right. And if you've ever tried to do this manually, which to say that I have any parameter and just automated as fast you possibly can, you might have noticed in any dog that there's kind of a limit to how fast you get botulism and you might not notice, but he might be news to you it turns out there's a little bit I don't know what or why, but for some reason just cannot directly modulate something just with regular automation sources very quickly has something to do with processing. I personally don't know what but there's a way around this and this way around it is the way that every single fm so this works and also every kind of fm in other sense, like some sense like, uh diva or massive they integrate fm is part of how they work and that fm, while not being the main purpose of that since, still works the same way as every other fm, same as syrup as well and that's f event in integration, but the way that imagines to solve being able to modulate so fast as actually the exact same way that the yamaha dx seven does it, which you might be thinking well what's up with that because the yamaha dx seven is a piece of hardware it is piece of hardware but it's also a digital processor it um it was the least I think it was the first of its kind to be able to use fm in a manageable way and we don't know what I mean by manageable way how is this not manageable? Well in the real world I say the world turns of like and along synthesis also there's just oscillators and you can play again on center in another house later and I will just do it put put it on the pitch the other also later and a little modulate it all day long but one of the kind of the sort of eccentricities of analog hardware the people towers being you know while the reasons whether better is that there's never really perfectly a pitch it's not completely perfectly controlled ordered phase fat matter and it's hard you know that the very fine fine tuning level to keep it you know together which for most applications is fine does that super important but you might notice in the grid for citrus that you can have lots of chains of routing and in these gigantic chains of drowning anything changes in pitch even just a little bit it will radically changed your tone and even make it something that's kind of unusual and very in harmonic and bad something which could be kind of cool to do but that's all you're able to do then you're sort of limited in terms of the process and it's not super great but the yamaha dx seven is digitally controlled oscillators and the way that the benefit of this means that it is always perfect and as we know the robotic clinical clean this of digital process like that kind of thing I think is there was it doesn't it doesn't process it doesn't actually mongolia pitch directly and solve this processing hurdle by modulating phase instead which was for some reason functional way no why honestly but I just know that split does is that it much let's face and now you might be thinking why does it do that? What is the purpose of modulating phase and how does that make it monthly a pinch because we totally saw a bunch of the pitch when we look at the sign wavering slowly um and you might be thinking, well, what's the difference why does that matter? And the difference become somewhat clear when I change the modulator from aside wave to a trying a wave? It doesn't quite seem like what a triangle life should do in fact, this behavior that's closer to what a square wave should look like in fact it looked like a square wave does e kind of weirdness and it's always way back, trying away way of all the various kinds of labor force you could throw at it you know the four main types of them all the side way was the only one that seems to do wet supposed to do and this has to do with you know what happens when you're modulating phase and the first the first kind of concept that you want to try to wrap your head around the idea of changing phase actually changes pitch um it's actually kind of like it's it's basically a little miniature the universe where we're doing our own little doppler effect and if you're not sure where the doppler effect is is the kind of thing where like if you're the example the books give you when you learn about it is you're standing in the road and a car comes by and the honking the horn and like it gets sort of hiring pitches he's closer to you in the lower pensions gets farther away that kind of thing that's that's about for a fact because the sound itself isn't actually changing pitch but because it's moving towards you the the starting phase of the sound changes and it sort of compresses the size of the way for which thanks a higher pitch or if it's moving further away from me then the same the same thing the way form is pushed outwards makes it sound like slower and this is exactly what happens when you change the face of something while you're playing it, which is very important because I can't do this manually. I can, uh, in citrus go to the phase and length the parameter to modulator exit over here, and I can change the face of one playing it but know that if I just change, phase and then stop and then play it the pitches and change the phases changes, you could tell because it gets snappy when it's not actually starting at zero crossing point, but then, while I'm blanket fast enough, it actually does sort of changed a pension, a very kind of unclean and dirty way because of, uh, control or alias thing and separates move. But the point being is that if you the pitch on ly changes while it's moving, so with this idea let's, look at the way forms again and why they have the effect that that that the deal I'm, uh, on the part of the population so sideways, if you look away, look away form of a sideways, it begins to barter view here it begins pretty quick immediately is moving pretty fast, but as a reaches its peak is that it was actually point where it's not actually moving anymore for just a second and that's when it arrives at that one that's actually the original pitch because we're moving in face it's in a different phase but not moving and moving and face and then azad its fastest was moving between zero process which is where the pay the fit the face changes different the fate of the pitch is different and then you look at the trying away way see that there is a speed on one single unchanging speed and then is another single unchanging speed and so we get one unchanging pitch that another unchanging pitch and mathematically what this turns out to is that the pit the change of pitch is equal to the change in slope of the way from that we're looking at um so this case the slope is one and then minus one and that one and that minus once was justice the sound, the sound and then the sideways it's the slope is changing so that the picture is changing and changes that one over again. If you get the triangle where does this always rather it is just the one pitch over and over again and then it tries to reconcile the snap in the the really sharp of charges that the change of solid position so it is just one pensions a different branch poses one pitch and then square wave is just flatness and then a snap of the flat listen that are snaps of just original pitch which is not to say that modulating bias always but by a swear wave is actually useless it might be in terms of changing pitch, but those snaps actually do kind of apply themselves in an interesting way uh when you use with other way forms it's a little bit painful sometimes it actually just in general and again if you ever tried messing around with that pham without really looking into what you're doing, you might have discovered that it's actually among the easier kinds of so this is immediately make something that can hurt you and sounds bad and not really feel good and even after that, you know what you're doing it's actually kind of hard to find the few uh if you sort of set ups that result of unusable the wall, we'll get a bunch of those today as well uh, yeah, so uh now knowing this is pretty important because in the analog world when we're just plugging way forms of the otherway forms, the movement in pitch is just what the way forms are. So if I put a sol wave in into a sign wave it would you know, you have a pitcher go down and they would stop picking back up we will go back down to stop picking back up like that's, what it would do and everything people based on what we looked at with how controlling faces a bit different, I want to even do that how would I make the way for move like that if I wanted to and you still can, you have the kind of thing you think about it in a different context with the idea of a slope change. So look to the side way, for example, on the slower side wave, it moves up and down, you know, the regular oscillation in the normal way that you think it should, but really what we want, when we want the sort of the the sorrow of activities that we wanted, we just want half of that we'll have to go down and then just keep going from up to down or down, up, you know, one way they are, and you actually can't do that and that's with the way for modifiers that exists in the window up here and f a mate there's actually entirely separate wave forms, they're called t x wave forms that just have these shapes, its for this purpose and the prayer, this specific example specific specific example, you just used the half modifier, it will basically do what he was doing in the way that we described, and if I wanted to make right now it's going up, if I want to go down, that reversed the polarity of the reading you might have thought of the direction of the routing that I chose over here actually determined what office later it was it was modifying, but all that means is just positive or negative modulation of the specific running that isthe and every every matrix kind of works a different way, some are clearer than others like f inmates is kind of clear words because it has arrows, and you could tell what you're doing here. We get lost, and citrus is if you mouse over what it is, and then you look at the upper left hand corner where sort of displaced information, you know, I should tell you specifically what that knob does, but for the most part, like, I mean, you get used to it it's, not that confusing, although it might be hard to explain to other people. So, do you have any questions about anything we discussed so far? You actually answered the question that came in about that right now, so we have we do have one more question. What would you recommend to emulate the moge cp two fifty one control processor? I don't know that is so I would not know, although just a sort of in general the idea of hardware emulation like aa lot of it, you just have to kind of think about what what is trying to accomplish because for example the idea that we could call the process reagan modulation would you have the our table here? There's ring modulation that there's ample to modulation on dh there is a difference between brig modulation appleton population and the only difference between the two is that ring modulation is a bipolar process where amplitude modulation is a is a single just just positive or negative depending on what? How you writing it? But the reason why it's called ring modulation in the first place is because of the hardware configuration that created the behavior was a circuit in the shape of a ring where you said that through and it goes around the big circle of that causes the volume to be bipolar up and down over and over again kind of thing. So it's like we the process the digital process that creates that I had seriously doubt it's some kind of emulation of there being a ring somewhere just the idea that our brains to fly above a downed bipolar so that it does that so whatever it is that that particular controller actually did um for the most part you might you just wanna just wanna try and find, you know, the result of that scene you could do that process. I know that most of time when people are trying to get go for and log emulation that they want the kind of we were describing earlier the eccentricities of their behavior and written realizing that kind of thing which might not stack up with the perfection of just having digital control but call it that means unless you find someone that does model it is that you're just gonna have to introduce those imperfections yourself, which could be a bit difficult because trying to start trying to be random on purpose, which is a physical impossibility if I remember high school, any other questions was extremely out there one particular one I think we're good all right on to do so um in a while the editorials that done with citrus I've tried ted tried toe sort of run home on the idea of that every defensive at its core is the same they all work in same way of the yamaha dx seven work in fact, you could load says x files from the yamaha dx seven into citrus and it will create the patch that it would have created with the yamaha dx seven same thing with ever mate same thing with toxic presumably is just it's all very, very similar. Um citrus is a bit more kind of like that generalized hurt in the process because I could see they have these way for modifiers that just changed what everywhere we've you've got into what you guys versus f inmates locked in, you have the list of way forms and there's so many reasons why I think it's just better, but you could still do. The stuff that I do with citrus would ever made was because of it has the basic way form has the routing and for the most part, it's the same, which is you have to you understand about the basic process that you should be able to sort of tow tub emulate that with whatever anything given even the you have a hot date. Seven south, although that big cat difficult, it's, because that interface is a bit odd, like, um, and the whole idea that the rain modulation matrix that is the whole secret deal, something entirely but like I did mentioned the idea that the idea that the volume controls the amount. So if I have, I have this knob that represents, you know, that sideways way do this thing there. If I wanted to automate that I can't automate this not this isn't it's, not really a knob stairway thing, it's just a setting for how much, and even if I wanted to, he does, however, moved it there is that kind of crackly, weird there's a number of ways to link sort of the value of the operator. You could just go the volume itself in this way. The volume knob is a one hundred two negative one hundred jobs of off center, so you have, you know, you pull in any change there, which is helpful for that kind of innovation is also the model. The way that city's works is that you have the parameters tab up top and then various modifiers beneath that it's not actually that different how harbor works because it was designed by the same guy uh, just ten years apart. Um, so you can link this to the modulation ex wheel up top ram where it is called the modulation wheel is the modulation x y matrix, even though and that is also sort of the monitors are there's a modulation tab and just for confusion sake, I referred to this tab was the modulation tab and the mod down here is modifiers to keep it in a different sort of brain space because it can't be a little both called mod and they don't mean the same thing. So it's a bit of a bit of a thing there, but what does the bob tabb do? Because if volume controls did a vigil oscillator that that's cool that we really needed to much more much else but what happens when you have, like, you know, all the oscillators all modulating, you know one thing, if I want to automate that I could individually automate every single one of these guys to do it want to do and really his lead the malt ahmad x and that that's finds the end of that or I could go to the mod tab of oscillator one and what the mod tab does is it controls the overall fm into that one also so no matter what activities happening in in the matrix um if I controlled the overall modulation and put into operation one little control the level of all the combined so you have been doing, you know one also it is worth of work to control the rest of them which is just a nice convenience uh there is an effort made there is a way to link the routing level two like the mon wheel control and then you khun automate that zika sesay parameter and many um there's other otherwise is internal modulation of her and well being and stuff like that ever made is just a little restrictive and how it works in terms of that in my own opinion, even though it is wildly popular um also it saw waivers weird overview ever noticed that but it seems the lack harmonics although for the purpose of using fm that makes sense because this means that's not, you know, complete thing is what you're creating that clicking sound that we exhibit would meet when we try to do with citrus such is pretty much is sort of like the no worlds one it just does what it does uh that's up to you to determine whether I wasn't good indeed any other there are a couple things I do I do I will kind of benches and when I get teo specific sound design examples of using fm for very like regular sort of sounds any questions accumulated there's one question about is it possible to emulate vowel filter like behavior in citrus or fm synthesizers in general valve builder yeah probably um actually this might be a reasonable time to bring up the idea of phase distortion again so the idea that we mentioned before is it's part of what I have discussed how because we do the drop like fellows general where you have ever felt there anything moving around that that doesn't think if you if you notice that when it when I did I would have done the lot think the big stock fell three one bad passes about a lot of stuff um it kind of muddied up the sit in a single day that really stay avery together so I don't find it at the end but again the signal I think there's a reason why we're always doing separate subs in that kind of thing for basic processing because it's constantly very muddying up lohan and phase distortion is something that happens even in a static but when you're when you when you're moving things again, remember which we were, when you change the phase of a sound while you're playing the sound it's going to change the pitch of this out and that's it that's probably not what they mean when they say phase distortion, but that differently is distorting, you know, the phases something while you're trying to play something. And so this means that when you're using traditional filters and you're doing that kind of thing, that some of the jet look out for it and I guess it is going to try and model a specific kind of, um, felt their behavior that you'll need to sort of look at what it does to the phases something's, unless you're using like a linear phase filter or using hgh, armor's additive filtering, which is about has the same sort of reaction is love your face, which is to say, doesn't have it is impacted phase it all, it's, all very static, most the time anyway, that probably didn't answer the question, but that was just kind of interesting thought to have on the matter.