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