ADLPlug: FM Chip Synthesizer | Hacker News Reader

ADLPlug: FM Chip Synthesizer

github.com

73 pointsdanbolt17 comments

I recently got obsessed with some music made for the OPN2, one of the chips modeled here - Yuzo Koshiro's soundtracks for the Sega Genesis:

Streets of Rage 2: https://www.youtube.com/watch?v=E5g-QHq925o

Streets of Rage 3: https://www.youtube.com/watch?v=kRrf-WxRsgs

The SOR3 soundtrack in particular showcases an avant-garde edge, closer to Autechre or Aphex Twin than traditional video game music, and generally more of a "club" aesthetic than anything I've heard in other 90's game music.

SoR1 is positively legendary for its soundtrack. On a good home hifi it sounded fantastic, and it contributed greatly to hammering-home the not-a-cartoon aesthetic of the gritty street brawler. Previous brawlers in that aesthetic were Final Fight and Double Dragon, but they lacked the neon glow, street punk clothing, and hard-thumping rave/dance sound track.

It's a shame that SoR4 sorta missed the mark on that. It just didn't really snag the simple clarity of SoR1's basslines.

https://www.youtube.com/watch?v=5Lp0GJNTRV0

These got a vinyl release recently https://bleep.com/release/72066

For some background—the Yamaha FM chips were fairly clever. Tie together an adder, some lookup tables, and a few registers and you’ve got sound. In particular, no need for a multiplier! The spartan design is the reason why they could release such inexpensive digital synthesizers in 1983, and then stick them in PCs and consoles.

People still write songs or develop games to be played on retro hardware, and having a VST plugin for the Adlib means that you can easily use your favorite DAW to write the track, and then export the MIDI file for playback on real hardware or in your demo or whatever.

That's really interesting. Would you have some more information on how the Yamaham FM chips were implemented. I'm still trying to wrap my brain around what "modulation" is actually doing and why it sounds the way it does when one wave operates another.

Your basic core is the numerically-controlled oscillator, which consists of a phase accumulator and a wave shaper which converts the phase to the desired wave (basically a sine wave lookup table).

    phase accumulator -> wave shaper

Yamaha FM just lets you add other signals to the wave shaper input:

    other signal -------\
                         (+)-> wave shaper
    phase accumulator --/

For example, instead of getting sin(x), you get something like sin(x + sin(x)). You start adding parameters like “a sin(b x + c sin(d x))” suddenly there are millions of possibilities.

“Why it sounds that way” can get really deep if you like, but basically, as you increase the modulation level you get more harmonics, and if you increase it too much you start losing the fundamental frequency. This is one of the reasons why it’s nice to have a 6-operator FM system (like in the DX-7). With the 4-operator FM, once you turn the modulation “all the way up”, there’s nowhere to go, but with 6-operator FM you have some extra operators around for modulating modulators.

The math is just Asin(at+Bsin(bt+...))+Csin(ct+...), where you can slowly play with A, a, B, b, ... but to get a good musical intuition try this tutorial for the Yamaha Reface DX (a modern incarnation of this algorithm, identical to the DX7 except they replaced the last two operators with a feedback unit per op instead of just one): https://www.yamahasynth.com/synths/basics-of-fm-synthesis

You may want to give this a read when you have the time: written by the man who discovered FM synthesis, and intended for musicians rather than mathematicians. Very eye-opening for any casual synth enthusiast--even somebody without a DX:

https://libgen.is/book/index.php?md5=A0BE23E763754D12807CDD6...

The book is long out of print so I don't think anybody would object to the link.

You need multiplication, but you don't necessarily need a multiplier. The trick was to do everything with the log of the signal, so you could use additions instead of multiplications, and then use an antilog lookup table at the end.

The sound was pretty lofi by modern standards, but it had a kind of pseudo-acoustic bite and slap that made older analog synths sound like mush.

The DX7 series of synths hit a sweet spot between being too clean and being too grungy. Game FM tended more to grunge. The later and more complex versions FM synths sounded a touch sterile.

A descendant of the tech is still being used in Yamaha synths today. And if you want to play with a VST emulation, try this:

https://asb2m10.github.io/dexed/

Does anyone know if there is a *nix-based app that supports these synth plug-ins?

ADLPlug can be used has a LV2 plugin which is supported by most DAW on *nix (Ardour, LMMS, Zrythm).

I think any Linux software synthesizer that supports VST or LV2 plugins should work with these plugins. The Wikipedia entry on Software Synthesizers lists several. https://en.wikipedia.org/wiki/Software_synthesizer#Linux_syn...

A search for "linux software synthesizer" should provide even more lists of compatible software.

You should rather ask if there's a -nix app that supports these well. I've not worked on audio on the PC for over five years, and had basicly stopped already once I switched over to Linux ten years ago. At the time, audio on linux was still literally a joke, though perhaps getting better. I wonder how far it got. I'm sure there were people with comfortable setups back then (e.g. Panic from Farbrausch, see Masagin from Farbrausch), so there will be people with positive experience now.

I think what bothered me the most was that the Ubuntu package for the Berkley collection of Synths was simply broken. Audacity frequently crashed. The DAWs weren't to my liking, but I'm biased on that point. I never saw through Jack, Pulseaudio and what not, which was really the running gag because it was--and probably still is so messy. Responsiveness in realtime fidelity was a real problem, too, I believe (similar for web based experiments).

it's a fair guess that server OSes like the BSDs won't have a better story

the JACK ecosystem is in an excellent place right now. i HIGHLY recommend the kxstudio applications for a smoother experience: https://kx.studio/

cadence - manages the JACK server and sets up pulse/alsa/midi bridging

catia - JACK patchbay

claudia - tool for setting up persistent JACK patch configurations

i'd also like to take this time to say that falkTX, the maintainer of kxstudio/jack1/jack2, deserves a medal for all his great work

https://kx.studio/Applications:Carla

this is the right answer-- carla is an incredible application. ADL/OPNplug also have standalone versions that work as JACK clients

Thanks, I'm a big fan of FM Synth music. Hoping to one day do some experimentation with the chip myself if I can find the time.

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