Wednesday, April 15, 2015

GEEKSPEAK U: The Yamaha FM chips of Gaming - Part 12 of 12: YMF292 (aka SCSP - Saturn Custom Sound Processor

Happy Tax deadline day to my US readers! :-)

This is our final installment of the FM chips series, and frankly, I wasn't even going to do this one. Why? Because I have yet to find anything that's music on the Saturn that is 100% confirmed to be FM.

What gives?

Well, the FM on the SCSP is a REALLY interesting animal. And when I'm done explaining it, you'll see why I say it is by far the MOST powerful, and yet, the LEAST powerful (or at least, the least useful) of all the FM chips.

Here's how it works. The SCSP is a 32-channel PCM chip, but each of those channels can function as an FM operator as well. NOTE: I did NOT say FM channel. I said FM operator. So, if you wanted to have a four op FM voice, you had to slave four channels to this voice. That means to replicate the functionality of the OPM (which if could do perfectly), you needed to tie up all 32-channels just to have the 8 channels of the OPM. If you wanted to replicate the OPN2, you had to tie up 24 channels with eight free for other stuff. If you wanted to replicate the OPL2, then you had to tie up 18 or 22 channels (depending on "drum mode" on or off) with 14-10 channels free for other things. Replicating an OPL3 would be impossible since you'd need 36-38 channels and you only have 32. OPL4? [In my worst fake New York accent] "Forget about it!"

So, when a) you have to tie up two-to-four channels just for one voice, b) you had such high quality sampling available plus post-sample effects like envelopes etc that it's virtually impossible to distinguish "sampled FM" from "real FM", or could just stream PCM samples of FM or use rebook audio, and c) it takes a whole lot more programming work to get the four channels to work together properly than it does to slap down a sample, it's so EXCEEDINGLY impractical to actually use real FM that like I said, I have yet to find anyone absolutely confirm its use as music instruments. I have had a few instances confirmed as sound effects, and have had have a few instances confirmed using the FM function in the sub sonic range as an LFO on music and sound effects...but that's it. No real FM used for music unearthed (so far) even though there are a lot of "FMy" sampled sounds used in Saturn music.

This is why I say it's the LEAST powerful, or at least, least useful FM chip in the bunch. Essentially worthless in any practical sense as its [shall we not say] "robust" usage demonstrates.

However, the great paradox here is that in a theoretical sense, in terms of what the chip actually "could" do, it is so far and away above and beyond ANY of the FM chips we've looked at.

Consider: OPM, you could do anything you wanted with one waveform on up to four operators on a given channel. OPL3, you could do anything you wanted with up to eight waveforms on up to four operators on a given channel. With the SCSP, you had a virtually limitless variety of eligible waveforms (as far as I know, you could even use a PCM sample as your waveform, so "FMing" PCM, and all the tantalizing possibilities that entails), plus, you were not constrained to the number of operators you could use on a single voice (up to the 32-channel limit of course). So, while it would probably sound absolutely TERRIBLE, and while it's be incredibly impractical, if you wanted a single 32-operator voice with complex PCM samples as your could do it. Heck, for perspective, even the venerable Yamaha DX7 music keyboard (YM21280 - OPS) could not do anything even remotely like this, being instead "just" a 16-channel, 6-op, straightforward FM chip. Heck, OPS was even sine-only. From the documents I've read, though, if and when SCSP did use FM, it pretty much just kept things to four-operators.

So, unfortunately, I must end this series rather anticlimactically, and leave you, not with music that demonstrates the amazing powers of this most peculiar chip, but rather, with videos of a simple (early 80's TV sounding) jingle being played over and over again with different FM parameters, not seeming to use more than four ops a voice, and only using basic or quasi basic waveforms for the operators (much of this sounds very OPM to me). I'll also include a video of them scrolling through available waveforms, and most of them are not sine, so if the FM parameters used in the jingle are these waveforms, and not just sine, then this is indeed going beyond what the OPM would be capable of.

I hate to use something so simple to demonstrate something so powerful. It's like letting a lion out into a very small cage...but on the other hand, as far as I can tell, appealing to actual Sega Saturn music is like not letting the lion out at all. At least this is real FM really being done on a real Sega Saturn...


PS. Thank you for coming along with me on this journey through the FM chips of Gaming! I hope it was equal parts educational and entertaining ("Edutaining?"). And I hope it will help you see - and hear FM in a whole new light...or at least with greater depth and clarity.



  1. Hi there. Just read through the series today. Best summary / comparison of Yamaha FM gaming chips that I found on internet. Edutaining indeed :-)

  2. Thank you very much Soundust! I'm sorry I didn't notice this reply til now!

    I am glad someone besides me finds the matter fascinating! It's so interesting how these chips are ultimately all so similar, and yet, are all so different too! And the video game music made with them all is so very wonderful too! They were all used to such amazing effect!

    Thanks for reading! BTW: At some point I'm going to dust off an old series I wrote for an online gaming mag back in 2012 about the 16-bit console wars, and touch it up and ready it for blog format. I also want to write about the current gaming scene from a sorta "Nintendo Switch vs the World" perspective!

    Stay tuned! In the meanwhile, there's always the podcast! :-D