It was Dr. John M. Chowning who first discovered FM synthesis in the late 1960s. As a musician and composer, he was already working on his pieces with a computer system at Stanford University in Los Angeles. The sounds of the system were very sterile and he wanted to give them a bit of a boost and tried to do so with vibrato effects.
Although the computer available at the time was cutting-edge, it only offered simple sine waveforms, so Chowning experimented with two sine waves to which he assigned different pitches. The results were always a long time coming, as it took a while to calculate the result. This led to the magical moment when two sine waves connected together produced a completely different waveform, such as rectangles and bell-like inharmonics. So instead of continuing to use vibrato to make sterile sine sounds sound livelier, he shifted his experiments to generating different waveforms by means of linked sine waves and their tuning ratios to each other. The first results were reminiscent of the additive synthesis already known at the time, i.e. overtone spectra, but which could be produced far less expensively.
It quickly became clear that it was possible to create sounds that were reminiscent of conventional instruments, such as trumpets and flutes, instead of the typical synthetic sounds that analog synthesis was and is known for. At the beginning of the 70s, the matter was ready for patenting and not much later Yamaha became a licensee. The rest is history, because nothing has been the same since the Yamaha DX7 synthesizer. And since then, musicians have been trying to create their own sounds with this FM synthesis. Most of them don’t succeed, having previously been told that this FM synthesis is difficult to understand. But that is not true.
FM synthesis is basically simple. And why do so many musicians fail to get to grips with it? Because you can’t learn FM synthesis, you have to experience it for yourself. Preferably in a playful way. But not completely without a plan. And you also need time. There’s a good chance that this will happen at some point, just like with chowning: Suddenly there it is, the magic moment. When the penny drops and you realize: Oops, that’s how it works?
Yes, that’s exactly how it works. However, it helps to have a little knowledge of acoustics, conventional musical instruments and, above all, patience and the drive to want to get to grips with FM synthesis in practice. Oh, so real work? Yes, but if you’re really serious about it and enjoy exploring things and just won’t rest, trusting that it will happen at some point. When will that be the case? They’ll know, guaranteed.
It’s about vibrations. Slow and fast, a combination of both. Carefully tuned and also randomly thrown in. Those that resonate with each other. And some that are brought to life through dynamics. The ear, with its highly sensitive ability to recognize the finest or coarsest movements and differences in temporal expansion, can show itself from its best side.
Chowning once said in an interview that you program an FM synthesizer with your ears. And that’s exactly what it is. You simply listen carefully to what you do with the parameters. Over time, you gain a wealth of experience that helps you to proceed in an increasingly targeted manner. The order in which you proceed is something you decide for yourself. FM is frequency modulation and that literally says it all. You are only dealing with frequencies that you can impose your own will on. You can determine their color, influence the duration of the sound development, whether any changes should take place over time and how dynamic control can influence it at any time.
So, we are talking about frequency modulation with only 2 operators. The operator with the carrier frequency is modulated by the second operator. So there is a relationship between these two, like two people having a dialog with each other. The tuning of the modulator therefore influences the sound of the operator that delivers the carrier frequency. Since the pitch of the modulator is normally set with the parameter Pitch or a similar parameter designation, you have a long list with which you can create almost any waveform. It doesn’t have to be an even value for Pitch, you can also use odd values.
All of this can also be found in nature. Ocean waves are created by deep trenches in the deep sea, plus winds above the water surface, both modulate each other and currents are created. Frequency modulation at its finest.
It doesn’t take long to realize that a large number of different waveforms can be generated with 2 operators alone. This does not include the frequencies of the carrier. Because this can also be tuned, just like the modulator. Given this multitude of possibilities, is it easy to lose track? Indeed, it is. FM synthesis instruments usually have more than just 2 operators, the DX7, for example, has 6 of them. So how do you keep an overview? Firstly, by getting a few empirical values. A ratio of 1:1 simply provides two sine waves, while 1:2 gives you a square wave. And so it goes on until it gets into the inaudible range.
Once you’ve done this a few times, you’ll automatically remember the waveforms that you particularly like because you use them in your music. And others that somehow deliver the opposite, i.e. sound like they’ve been brushed against the grain. If you constantly play any phrase on the keyboard during these pitch experiments, you can immediately check what a currently set waveform is suitable for and which is less so. If you want to do more, try the carrier instead of the modulator and try out all possible ratios in relation to the modulator.
The bottom line is that theory and tangible practice work best together and are therefore easily memorized. A little trick here is to be decisive. No matter how many options there are with this tuning, you simply save a reasonably suitable waveform. This will definitely help at this point for later approaches. This way you create a pool of candidates. You can continue to work on them later when it comes to creating complete instruments.
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