FM synthesis has enjoyed a surprising popularity and longevity – from the inscrutable but best selling DX-7, a plethora of cheesy OPL sound cards for game consoles, a rabble of ugly virtual instruments, expensive European groove boxes… all up forming a very successful career – despite near to no owners ever creating their own sounds.
Behold – I AM the Anti-Knob.
Today’s FM is more complex but much easier to control than the DX-7. The language of FM has developed to include many changes. Here’s some highlights:
- 1978: The Synclavier was first to market, with FM under license from Yamaha. Their own GS-1 would follow in 1980. It had eight operators based on sine waves.
- 1983: The classic DX era had FM based on sine waveforms, with six operators in the DX7 and four in the DX100. No filters! No sir.
- 1987: The TX81z added additional waveforms to augment a four operator system. In general these were equivalents to traditional saw and square waves.
- 1989: The six operator SY77 and SY99 had additional (but different) waveforms, as well as samples. But they now had a filter, a concession to mainstream. Did it work…? Perhaps not.
– a long gap and then – - 1998: The FS1r added many features – eight ‘voiced’ and and ‘unvoiced’ operators using eight ‘spectral forms’ instead of fixed waveforms, which included a resonant peak with an adjustable skirt. And filter. The machine was a huge failure – but the formant technology would resurface as Vocaloid, and eventually came …
- 2016: The Montage which introduced an oddly familiar FM-X.
FM-X
So what is FM-X? It’s obviously based on the eight operator system of the FS1r, but with more hands-on control of the spectral forms in real time. The marketing is more about the flow now available between different FM settings to create long morphing sounds. The anti Anti-Knob.
The 7 spectral forms are much as they were for the FS1r:
- Sine – a single pure frequency as found on the DX7. Classical FM.
- All 1 – a sawtooth formed from stacked sines
- All 2 – ‘narrow’ version of the above
- Odd 1 – a square wave from stacked sines
- Odd 2 – a ‘narrow’ version of the above
- Res 1 – a peak frequency positioned in the stacked sines – a formant.
- Res 2 – a ‘narrow’ peak frequency in the stacked sines – again, a formant.
Spectral Skirt sets the width of the frequency range while Spectral Resonance sets the amount of the distortion. Far more vocal/nasal/resonant body then before. I’ll show the official diagrams.
Halion FM Lab
The cheapest way to get FM-X is Steinberg’s Halion. While Steinberg is now part of Yamaha, the developers are largely autonomous and have created a compatible variant. Forgive me for any errors: It’s been difficult to make out the differences (without buying a Montage no thanks). You can load and edit FM-X patches. You can also open patches for the DX7, TX81z and SY99 simulating the waveforms that came with those. There are extra traditional waveforms that I can’t find in the Montage documentation. Saw, Saw Rounded, Square and Square Rounded are also modified by the Spectral Skirt control. It seems that you would not be able to import back to the hardware.
Many of these changes (filter, saw waves etc.) have dragged FM back towards traditional synthesis. Perhaps the purity of the idea never translated into artistic reality. In any case it’s useful to create a traditional sound and then have the luxury of warping it with FM manipulations.
Altered FM
There are now many non-Yamaha variants to try.
Roland dipped into the water with FM oscillators on the System-8. They’re quite simple – just fixed ratios with a level control. A similar set up appears on the SH-4D. It creates pleasing old school FM boings, but not much new.
KORG gained access to FM when part of Yamaha, which they identified as Phase Distortion and bundled into the DS-8. FM also shows up as ‘MMT’ on the RADIAS. (Strangely enough the phase distortion used by CASIO was different again.) A similar voice is found on the Minilogue XD.
KORG have recently developed Altered FM for the opsix keyboard. You have algorithms and operators, but an ‘operator’ now includes a wide range of effects, filters, traditional synthesis elements in the algorithm – more of a modular synthesis concept. It can sound like a DX7 as much as a Moog and many shades in-between. Very recommended.
Tone2 offer Nemesis with something called NeoFM synthesis which is ‘an exclusive and improved approach to FM synthesis’. To my ears isn’t really that different to FM but I think I might be holding it wrong, the interface not quite making sense to me. It uses sampled waveforms in the operators which are also combined in a wider variety of schemes – so on paper it should do all the things FM-X does.
The last link might be a bit controversial. Because when I look at the spectral controls on the latest Arturia Pigments I notice an odd resemblance between the FM Spectral Forms, Skirt and Resonance and the controls in the Pigments Harmonic oscillator. No – it’s not the same – but there are definite parallels in the tools in play. I think Arturia have drawn from a much earlier era than the FS1r, but arrived in a nearby place. c’est la différence.
Re “the phase distortion used by CASIO was different again”.
As you may recall, Casio had two types of “Phase Distortion” synthesis, the later one being “Interactive Phase Distortion”. Wikipedia (https://en.wikipedia.org/wiki/Phase_distortion_synthesis) maintains that the latter “bears very little resemblance to ‘actual’ PD, being based around an idiosyncratic type of PM instead” – Phase Modulation (PM) being Yamaha’s method of attaining FM.
No source is given, but the description of the VZ synths is accurate, and the VZs certainly sound very different.
IPD was essentially Yamaha’s FM with the serial numbers filed off. I much preferred the slightly more limited noises made by the “traditional” PD Casios.
AFM (as found on the SY7700) is pretty great if you know how to use it. Those three feedback loops are there for a reason and they will allow you to create proper sawtooth and square waves using just a single operator. With that as a starting point, it’s actually quite easy to obtain your bread and butter analogue noises with a little bit of practice.
Yamaha’s envelopes on FM synths, though, have always just sucked. They are powerful and the loop functionality is really cool for about five kinds of sound but it would be really nice just to swap them over to ADSR for most tasks, rather than building an ADSR from the multiple stages that you’re presented with.