GEEKSPEAK U: The Yamaha FM chips of Gaming - Part 3 of 12: YM2608 (OPNA)

The YM2608 (aka OPNA) was basically an OPN with three more FM channels (six FM channels), a dedicated single-channel ADPCM sampler, and a pre-programmed six-channel ADPCM "drum machine". That does make for a total of seven PCM channels, but again, six of them you could not load samples into, but only use pre-programmed (or "canned") drum samples built-into ROM. The one ADPCM sampler that was not part of the drum machine was a dedicated sampler, that could sample anything.

I'm not sure if this chip was used in the arcade or not, though it would've been the perfect arcade chip with a PCM drum machine, an open sampler that could be used for anything, and wasn't needed for drums, six nearly OPM caliber FM channels, and four PSG channels. If it was never used in the Arcade, that would be quite a shame - and it's a shame anyway since at the very least it was not prominent there. The only application that I'm positive about was its use in more advanced versions of the NEC PC88 / PC98.

Ultimately, it's going to sound VERY MUCH like a Sega Genesis, only it's gonna have more robust percussion (higher quality), and possibly a sampled voice or instrument concurrent with the percussion, whereas they'd have to trade off on the Genesis. Also, while both chips had six FM channels, the Genesis had to surrender one of those six for percussion (be that FM percussion or sampled percussion), so while both chips had the same number of channels, in practice, it was really six channels of simultaneous FM vs five. The PSG chip in the OPNA is different than the PSG chip used in the Genesis - and better than the one in the Genesis, but when they're both buried deep in FM, you don't really hear much of a difference between them. So in practice, they come out about a wash here. Still, outside of an actual YM2612/SN76489 FM/PSG combo, nothing sounds more "Sega Genesis" than a YM2608 OPNA.

Most OPNA music I've heard still makes generous use of the PSG. This soundtrack, "Zu Sukimu" (The Scheme), also by Yuzo Koshiro (like the Ys soundtrack we used for the OPN) does not. Also, it makes pretty prominent use of the ADPCM instrument sampler channel for sampled instruments, including a guitar at one point.

So it's quite an anomaly. What do you think?

Here are a few tracks on the OPNA that are quite a bit more "hallmark OPNA". I've got three tracks from a game called "Groundseed", and then one each from "Night Slave", "Nova: Miirareta Shitai", and "Rusty" - all three from the PC98.

Groundseed - Town 3

Groundseed - Akira

Groundseed - Shop Demo

Night Slave - Hard Rushing

Nova: Miirareta Shitai - NVo2

and Rusty - Queen in the Dark Night

GEEKSPEAK U: The Yamaha FM chips of Gaming - Part 2 of 12: OPN series intro and YM2203 (OPN)

The OPN line had several chips that were used. While they varied greatly in terms of how many FM channels they had, what kind of sampling and/or PSG capabilities they had, and the number of total channels they had, they all had this one thing in common with each other: their FM channels were all four-operator, eight algorithm, sine-only. Which means "on-an-individual-channel-per-channel-basis", the entire OPN line were all equals*. OPM had some advantages over the OPN line, namely the second detune parameters, and the beefier LFO. But sharing the sine-only four-op, eight-algo thing definitely put OPM and the OPN line more or less in the same ballpark in terms of raw "on-an-individual-channel-per-channel-basis" FM capabilities.

The first chip in the OPN line, the YM2203 (called "OPN") only had three FM channels, and no sampling capabilities, but it did have an entire YM2149 PSG built in. YM2149 is essentially identical to a General Instruments AY-3-8910, which had three pulse wave channels (almost exclusively using plain square waves), and one noise channel. Though this is a series about FM, and this is an "FM chip", it really is just as much a "PSG" chip, and that's the side of the house that will actually get more talk time in this post:

The YM2149/AY-3-8910 chip was very comparable to the NES' 2AO3 in terms of its pulse width options. NES had four modes, with a total of three timbres (since two of them sound identical to each other, and are thus redundant), 12.5%, 25%, 50% (square), and 75% (redundant to 25%). The AY/YM had 25%, 50%, and 85%, though again, the 50% plain square was almost exclusively used. Both had very good noise channels. And both could use periodic noise musically (though I don't think NES ever did this, except for the metallic voices in Quick Man (Mega Man 2)). I believe AY/YM used this mode more often. Both AY/YM and 2A03 could pitch themselves comparably deep.

The biggest difference between the two is a) NES is two pulse, one triangle, and the AY/YM is three pulse, and b) the NES, albeit a very, very crappy one, and not frequently used, had a dedicated PCM sampler channel, and the AY/YM did not. If it was going to sample, it had to do it by tricking the periodic noise to do it, which sounded even worse than the NES's crappy sampler, and tied up a channel, where all four of NES's "normal" channels would still be free during sampling. One advantage to the AY/YM, though, is that its square waves had this great haunting quality to them that the crisper NES lacked.

Anyway, that's the AY/YM vs NES in a nutshell, and the basics of the YM2203 (OPN) FM chip as well. I know we spent more time talking PSG than FM in this post, but as I said above, it really is about an equal component in this very "FM/PSG-duet" sounding chip, and the FM side, between what was already said in the OPM post, and the remainder of this series will be fleshed out quite nicely.

OPN appeared in several arcade games, and also in the NEC PC 88/98. Our examples are the Y's I and II soundtracks for the PC88, composed by the legend - Yuzo Koshiro, the Sorcerian PC88 Soundtrack and a standalone track from Advanced Power Dolls 2 for the PC98.

The first three are more typical examples of the OPN's sound, though the Advanced Power Dolls 2 track shows that the OPN is actually capable of quite a bit more advanced sounding things - in fact, I had originally thought I was listening to the OPNA, because I thought the drums were sampled - nope...FM. Also I thought there might've been more than three FM channels happening at once, but again....nope. You really can do some pretty amazing things on the OPN!

Ys I

Ys II

Sorcerian

Advanced Power Dolls 2 - PC98 - Believe in Motivation (composed by Hiroto Saitoh)