I would suspect it was a combination of keeping costs down and lack of a real need for it at the time.

FM synthesis in computer audio was short-lived. It was quickly supplanted by sample-based audio (e.g. wavetables, MOD/S3M formats) and then digitally recorded music.

And for modern chiptunes there are plenty of FM synthesizer options both in hardware and software.

As you say, OPL3 is effectively dual OPL2, which means a single OPL3 chip already gives you stereo and 20 channels.
I suppose dual OPL3 was considered overkill, especially since hardly any software ever went beyond a single OPL2 at all.
Dual OPL2 or pure OPL3 support is very rare.

By the way, a single OPL3 can already be set up as dual OPL2.

I think the OPL4 was already the perfect upgrade as a full OPL3, GM Wavetable rom bank, and up to 24 PCM channels with support for up to 4mb of sample memory. Problem was, sound card builders treated it like a low budget toy. OPL3 mode for FM and GM bank for MIDI. I don't think there was a single PC card with dedicated sample memory or the means to fully control the chip. Afaik there were no PC games that included an OPL4 required sound option.

SuperDeadite wrote on 2023-07-17, 05:10:

I think the OPL4 was already the perfect upgrade as a full OPL3, GM Wavetable rom bank, and up to 24 PCM channels with support for up to 4mb of sample memory. Problem was, sound card builders treated it like a low budget toy. OPL3 mode for FM and GM bank for MIDI. I don't think there was a single PC card with dedicated sample memory or the means to fully control the chip. Afaik there were no PC games that included an OPL4 required sound option.

Exactly. We have all heard all those cool tunes on adlib tracker for example and almost no game came close to have such a soundtrack. Sure there are some very nice game bgm but they do sound rather simple (but nice 😁 ).
Even OPL3 is underutilized in pc games, the vast majority does not go beyond OPL2 capabilities AFAIK. So a dual OPL3 board would just go to waste if it existed.

To my knowledge the best OPL4 implementation on PC was Yamaha's own SoundEdge SW-20PC card but even that had it's own problems like the terrible MAD16PRO sb-compatible chipset and the fact you needed to load a TSR to get OPL4 midi going under DOS... but it had some 128kb of user-sample SRAM, a nice 2MB GM rom bank and that programmable Yamaha FX processor going for it.

keropi wrote on 2023-07-17, 05:44:

To my knowledge the best OPL4 implementation on PC was Yamaha's own SoundEdge SW-20PC card...

In expanded form (that is, with the 512KB RAM and YSS225 daughterboards), Mediatrix' Audiotrix Pro is arguably a more-complete OPL4 reference architecture than the SW20-PC.

Cloudschatze wrote on 2023-07-17, 06:09:

In expanded form (that is, with the 512KB RAM and YSS225 daughterboards), Mediatrix' Audiotrix Pro is arguably a more-complete OPL4 reference architecture than the SW20-PC.

I had to google for the card 🤣
Does it have any gaming value? Any idea how it's software/toys look like?
I am very familiar with the SW-20PC as it happened to get it back in the day but I had no idea that Audiotrix Pro existed and is something different than the other audiotrix 3dXG something something 🤣

Hm. I was thinking of music mainly.
There are so many OPL3's around (chart), but for some reason, there's little to no joy of experimentation / eagerness of experimentation.

So many new Sound Blaster replicas, AdLib clones and XT motherboard designs, but apparently no interest to develop something new in this regards.
It's as if the DOS community/scene is stuck in the past or something. 🤷‍♂️

Quite a few replies said that OPL3 is good enough in terms of polyphony, but I think otherwise.
It's only true if we use the OPL3 as a pair of basic OPL2s.
But the OPL2 instruments/waveforms are quite limited in comparison to the OPL3's 4-OP mode.

But if you use 4-OP, you'll loose a lot of channels, so you end up with a handful
of channels with ambitious instruments
vs. a dozen of channels with simple instruments.
So it's a massive tradeoff that must be made.

I noticed this limitation when I compared OPL3 vs ESFM on Windows, as well.
The ESFM can handle complex MIDI titles just fine, while the OPL3 had its trouble keeping up.
And this was with the Voyetra SuperSapi synth, which is already a bit above the normal OPL3 synth driver.

The OPL4 is a fascinating wavetable chip with an OPL3 legacy core.
But it adds no new features to that FM core.
Still, it's nice if sample RAM is available. The MediaTrix AudioTrix Pro had it, I think.
The MSX community also used the OPL4 (MoonSound etc).

But MIDI is far from ideal for any kind of sound chip.
Trackers can get a lot more out of a limited number of channels than MIDI can.

Dual-OPL3 could be nice with two times the channels and registers allowing enhanced stereo effect. But I agree with most, it is not something viable as there is today very powerful software to produce synthesis music and there was no market for that in the mid-90's.
I would prefer an OPL4 based solution. Still an OPL3 for FM but allowing very powerful things through PCM banks. It's a shame no games used it. But with GS and GM MIDI modules around, I know why... About OPL4, do not forget the miro miroSound PCM1 Pro! Like the MediaTrix AudioTrix Pro, it uses a CS4231A, so they are "only" SB compatible, not SB Pro, meaning low quality monophonic PCM sounds in games. but 16-bit CD quality samples can be use through WSS I think.
For my part, I dream of an Orpheus with a YMF278B, would be nice for playing musics made for it 😉

Scali wrote on 2023-07-17, 10:04:

But MIDI is far from ideal for any kind of sound chip.
Trackers can get a lot more out of a limited number of channels than MIDI can.

I agree, it's just that I had no other means of comparison here. 🙁

If AdlibTracker II had a fork with ESFM support (and a few ESFM sample songs), I would have had a more meaningful comparison, maybe.

Unfortunately, the ESFM wasn't really accepted. It's not a bad OPL3 compatible per se, but it's not 100% authentic, either.
So I can see why FM lovers prefer a YMF-262 here.

Edit: Found something. ESFM had 18 four-OP voices in native mode.
There's even an attempt at emulating the chip.
https://github.com/Wohlstand/OPL3BankEditor/issues/164

Hm. Now that I think of it..
Wouldn't it be possible to combine two individual OPL3 soundcards?
One at port 220h, the second at 240h?

That way, there would be no compatibility issues?
Or is port 240h used very often?

I'm just wondering. It's a purely fictional thought.
If such a setup would gain popularity, polyphony could be easily increased.

Programs like AdLibTracker II could simply add a parameter for a second port adress/soundcard and introduce a slightly modified tracker format with a provision for the second OPL3.

And existing DOS games/their sound engines could be patched to support 4-OP instruments, without much alteration of the OPL3 score.

And if a TSR is written, the two OPL3s on 220h and 240h could act as two independent OPL2s,
thus providing Dual-OPL2 compatibility with full polyphony/number of voices.

That way, users could still "upgrade" by installing two old OPL3 Sound Blaster.
In principle, I mean. The DAC resources on a secondary card are an issue (running out of IRQs and DMA channels on PC).

A specialized Duo OPL3 card with a single SB/WSS DAC at 220h and two OPL3s at 220+240 would cause less trouble.

Jo22 wrote on 2023-07-17, 10:59:

Hm. Now that I think of it..
Wouldn't it be possible to combine two individual OPL3 soundcards?
One at port 220h, the second at 240h?

I think MIDITo can do something like that, for the purposes of mimicking the dual OPL2 chips of the SBPro 1.0.

Disclaimer: I haven't used this utility yet, so I have no first hand experience with it.

The train for dual opl3 or opl4 or <insert chip here> has departed
There would be no gain for old software and - let's not kid ourselves - there is not much new software getting released for old PCs.
So at best you might gain some support for Adlib Tracker that would possibly also need special tracks to take advantage of the enhancements...

Remember the ISA SID and SAAYM cards? They are available but what is their purpose? The SID card can run a few games and the SAAYM one to my knowledge is only used with VGM player to listen to md/sms sountracks. Nothing interesting came out of them and in the same way nothing interesting will come with a hypothetical superFM soundcard.
I would love to be proven wrong though but looking on other retro-scenes the most valuable upgrades are the ones that are working with the already existing old games and programs.

Shponglefan wrote on 2023-07-16, 22:05:

FM synthesis in computer audio was short-lived. It was quickly supplanted by sample-based audio (e.g. wavetables, MOD/S3M formats) and then digitally recorded music.

I wouldn't say that.
FM music was used for a decade, basically for DOS games.
While the AdLib soundcard has been introduced in 1987 the first games supported the OPL2 from 1988 on.
Better sound could be achieved with MIDI devices that used wavetable samples like MT-32 - due to the costs it was not widespread.
While the Sound Blaster Pro (Version 1) had 2 OPL2 chips to achieve stereo sound its revision (Version 2) used an OPL3 instead.
With the approach of the Gravis UltraSound 1992/1993 WaveTable sound became a greater desire. However, OPL sound still has been standard and both (!) emulators on the GUS (MegaEm, SBOS) were not sufficient and lacked in compatiblity too.
The spread of the Sound Blaster AWE 32 solved the problems by having both AdLib compatible FM synthesis and wavetable on the same card.
With the popularity of Windows95 and 98 the abstraction layer of DirectX PCs passed the need for AdLib/SoundBlaster compatiblity. At the time of Pentium, Pentium MMX and Pentium II the systems were fast enough to process wavetable music in software.
However, in the early 2000's there were still fans of DOS games, so users prefered a SoundBlaster 16 compatible ISA soundcard over the oncoming PCI soundcards....

I would say: DOS gaming = FM / OPL sound

keropi wrote on 2023-07-17, 11:26:

Remember the ISA SID and SAAYM cards? They are available but what is their purpose? The SID card can run a few games and the SAAYM one to my knowledge is only used with VGM player to listen to md/sms sountracks. Nothing interesting came out of them and in the same way nothing interesting will come with a hypothetical superFM soundcard.

Yes, on my TODO list is still an update of SoftIMFC to use a SAAYM card instead of an external Yamaha FB-01... but even then there's only a handful of games with IMFC/FB-01 support.

the more things available the better 😀

Disruptor wrote on 2023-07-17, 11:52:

Shponglefan wrote on 2023-07-16, 22:05:

FM synthesis in computer audio was short-lived. It was quickly supplanted by sample-based audio (e.g. wavetables, MOD/S3M formats) and then digitally recorded music.

I wouldn't say that.
FM music was used for a decade, basically for DOS games.

It was supported for about a decade, but it was mostly used as a backwards/downwards compatible option in lieu of other options. It's similar to how the PC Speaker was supported by games into the mid-90s.

Not a lot of soundtracks or even sound effects were designed primarily for FM synthesis. In that respect, FM synthesis was a relatively short-lived format.

This especially telling by the lack of stereo or OPL3 specific soundtracks in games.

I would say: DOS gaming = FM / OPL sound

This is true of late-80s and early-90s DOS gaming, but not DOS gaming as a whole.

DOS gaming covers two decades and a variety of audio formats and playback devices.

If I take Need For Speed from 1994 as an example: the entire sound track was stored as digital audio on the CD. It supported Sound Blaster, but didn't use FM.
If I were to look hard, there's probably earlier games that only used digital audio.
I know various ports of Amiga games, such as Pinball Dreams/Fantasies played back the Amiga tracker modules via software mixing, so also no FM.

Shponglefan wrote on 2023-07-17, 12:46:

It was supported for about a decade, but it was mostly used as a backwards/downwards compatible option in lieu of other options. It's similar to how the PC Speaker was supported by games into the mid-90s.

I think it was understood by game developers at the time that the vast majority of their customers wouldn't have access to Roland gear. They still primarily composed their music on Roland hardware because it provided the best results, but OPL3 wasn't entirely dismissed either.

Granted, some companies put more effort into OPL3 conversions than others, so many of those were subpar. But the ones that did it well (Interplay and Blizzard for example) had some pretty nice sounding FM synth music in their games, and it sometimes even used actual OPL3 stereo.

There's an interesting interview with the composer for Transport Tycoon where he goes into much detail about the music creation process. The original page on Gamasutra is no longer online, but the archived interview is still available on the Way Back Machine. Relevant bit:

John Broomhall wrote:

I’d already learned that writing on better sounding soundcards and then downgrading to a basic Soundblaster or AdLib card was much tougher than going the other way, so I started out on the humble FM cards and, once the tunes sounded as good as possible, I set about upgrading them for the Roland’s LAPC-1 and for their General Midi flagship card, the SCC-1. Then, because the other so-called General Midi soundcards of the day, from Turtlebeach to Gravis Ultrasound, were all slightly different, I tweaked and finessed a separate version of the midi files for each and every one of the main players.

Many other developers probably didn't put as much effort as he did, but you can see that some of them did care about FM synth music even during the mid '90s.