Retro Game Audio
Can you explain how the MSX2 sound chip works? I was listening to music from Metal Gear 2 and it's got some great sounds.

Sure! Metal Gear 2: Solid Snake on the MSX2 has one of my favorite computer game soundtracks from the 8-bit era. I’m not as familiar with MSX audio as I am with the NES, but I know a little bit about the soundchips they used and the general limitations they had.

A brief introduction:

MSX machines are a family of home computers from the early ’80s. Part of the ‘8-bit’ computer market, MSX competed with computers like the Commodore 64, Atari 8-bit, and ZX Spectrum. They were popular in parts of Asia, Europe, and South America, but mostly unknown in the United States. You can read more about the MSX here and on wikipedia.

MSX2

(an MSX2+ [image source]) 

For audio, the MSX2 primarily used the Yamaha YM2149 programmable sound generator. It is a variant of the General Instrument AY-3-8910, which was used in many other systems like the Intellivision, ZX Spectrum, Amstrad CPC, and more. It is also similar to the Texas Instruments SN76489, the competing chip that was used in the Sega Master System.

The AY-3-8910 Sound Chip

This sound chip has three channels of sound, comprised of square waves and a noise generator (you can read an incredibly in-depth analysis here). This video demonstrates a youtube user’s favorite MSX music made with this PSG audio:

But Metal Gear 2: Solid Snake used a sound expansion cartridge for more advanced audio. Known as MSX-AUDIO, the cartridge contained the Yamaha Y8950, a sound chip that offered 9 channels of FM sound (or 6 if FM percussion is being used), and included an 8-bit ADPCM sampler. If you wanted to compare the audio to another system, it’s kind of like a more primitive Sega Genesis.

Three different cartridges for MSX-AUDIO were made by Philips, Toshiba, and Panasonic. Here’s what one of them looked like:

MSX-AUDIO Cartridge

At the moment I’m having difficulty finding a complete list of games that used MSX-AUDIO in their soundtracks, but I know that Konami had several, including Metal Gear 2: Solid Snake.

Something I like a lot about the Metal Gear 2 soundtrack is how it embraces the synthesizer aesthetic. The introduction to MG2 has one of the most cinematic-like openings of any 8-bit game I’ve seen, and the music has elements of ’80s horror / sci-fi themes. I’m reminded of music by John Carpenter (Halloween, Escape from New York, Assault on Precinct 13) at moments throughout MG2, reinterpreted with a Konami-esque sound.

There was also another sound add-on for the MSX known as MSX-MUSIC, which used the Yamaha YM2413 sound chip. It also offered 9 (or 6+ drums) channels of FM sound, but it was more limited than MSX-AUDIO because it allowed only one customizable voice at a time, with the rest being presets (more information here). MSX-Music was a built-in feature on some of the later MSX models. Fans of the Sega Master System will recognize the sound as the same FM chip used in some Master System games. 

One of my favorite MSX-Music soundtracks I’ve heard is the MSX port of Final Fantasy. I generally expect console-to-computer ports from the ’80s to not do the best job converting the music, but I actually like the MSX version of Final Fantasy more than the original Famicom/ NES version:

Hi! Don't mean to bother you again but can I request how Super Mario Bros. 3 does the whole bongodrum/steel drum like sound? You can hear it clearll at the end of the music that plays when you lose a life. Thanks!

Super Mario Bros. 3 uses very lo-fi audio samples (1-bit DPCM) for those sounds. The NES’s 5th channel is dedicated to sample playback. Anytime you hear semi-intelligible vocals on the NES, like the “I’m bad!" from Bad Dudes, those are also samples. 

The sample channel has some odd quirks and uses, so I’ll save a more detailed explanation for future posts.

Hey now. Interesting reads. I've never seen anyone go into depth about old game soundchips. What's your favorite music from an old game? Like what inspired your band?

Hey Ken! It can be difficult for me to pick any single favorites, but I could pick a few systems and list some of the first things that come to mind.

  • Amiga - Shadow of the Beast, Space Hulk, The Secret of Monkey Island
  • NES - Magician, Journey to Silius, Wolverine, Castlevania III, Overlord, Mega Man 2
  • Game Boy - Turok 2, Ottifanten Kommando Stortebeker, CV2: Belmont’s Revenge
  • Sega Genesis - Ecco The Dolphin, Ecco: Tides of Time, Ys III: Wanderers from Ys.
  • SNES - Final Fantasy IV, Super Metroid

Although I’m not sure it’s possible to pinpoint an inspiration for Cheap Dinosaurs. I had a band in high school that covered VG music, and through playing shows I met a band called Chromelodeon that played instrumental prog-rock. They were the first band I saw using chiptune hardware in original music. Eventually I played drums for them… then later on we disbanded.

But my friend Dino from Chromelodeon started writing music that used the Game Boy more heavily under the name of Cheap Dinosaurs, and eventually that turned into a full band as well. It has some former Chromelodeon members and other chiptune musicians (animal style, chipocrite, an0va).

Most of us have a strong, shared interest in vgm and chipmusic, but when it comes to writing music it’s mostly up to Dino’s creativity. I’m happy to be in a band with someone that I feel writes very original stuff- I don’t think we’ve ever had a conversation about a certain band or soundtrack that we wanted to sound like. The closest thing to that might be Goblin, who scored horror soundtracks in the ’70s and ’80s like the original Dawn of the Dead and Tenebre, although I’m not sure we sound that much like them. We’re big fans of instrumental and soundtrack music, including vgm but other types of music as well. :)

I grew up with an Amiga 500 and 2000 and made mixtapes of game music as a kid, but it wasn’t until the late ’90s when my brother picked up an old NES that I found a renewed and deeper interest in this stuff.

Hi, love the blog. I was wondering, is there anyway that you can utilize the actual sound chip for a video game system to create a synth? For instance, to make something like the Atari Punk Console but with the Sega Genesis' YM2612 chip?

Hey, thanks!

Unfortunately, building a chip-synth exceeds my level of knowledge. I’m more familiar with the tools and software that you can use to compose for various systems, but not how to extract the chips for use in a synthesizer.

As I understand it, there are obstacles for certain systems that make this difficult. The NES and Game Boy, for example, do not have dedicated sound chips because their sound generators are incorporated into the main CPU. I believe the Atari Punk Console is named for sounding similar to the atari, but it doesn’t use the TIA chip or components taken from an atari.

I think this is why a lot of people find ways to control the audio of these systems with things like customized MIDI controllers without converting them into complete, standalone synths. (synthcart [atari], midines [nes], mssiah [c64]) 

There are also plenty of non-live/ non-midi options, that involve sequencing or coding music in advance and finding ways to run it through the system with hardware like the powerpak [nes], ems usb [game boy], and the everdrive [sega genesis].

But there are exceptions! The C64 has a dedicated soundchip, the SID, which has been fit into a variety of devices like the MIDIbox SID. I also just found a youtube video of someone who made a MIDI synth out of the Atari TIA without the motherboard. 

Mail Order Monsters is a group from Michigan that uses many synth-controlled SID chips live:

The Sega Genesis is a special creature because it has two soundchips (YM2612 [FM] and SN76489 [PSG/ “8-bit”], and many hardware revisions. The YM2612 gets integrated into another chip in certain models, so if there’s a chance to remove it and get a use out of it, you’d probably want to start with a model that has a discrete 2612. You can see a list here that distinguishes which have discrete and which have integrated.

I hope this helps! If you have more questions regarding the possibility of building the Sega’s YM2612 into a synth, I’d recommend contacting little-scale. He’s built many of his own midi-controlling devices for Sega systems and will know better than I. :)

If using the original hardware isn’t of utmost importance, the Yamaha DX synthesizers have a very similar sound.

Hey! I found you via Kotaku and I really think you're blog is awesome! I understand you might be busy with your own schedule and all, but do you think you could explain something like how a game like MC Kids makes a Commodore 64-like wiggly sound? Im not sure what it's actually called but specifically the Level 4 theme shows it well. I think it'd be great because I always wondered how that effect is achieved! Thanks!

Hey Jesse!

I believe the C64-like sound you’re referring to is the arpeggio effect, although there are a couple things about the MC Kids music that are reminiscent of the C64. I like to call this kind of NES music “Euro Style”, because of the direct impact the C64 had on Western composers’ sound design.

The arpeggio effect is chipmusic’s solution for simulating a chord in a single channel. It is very prohibitive to arrange “true” chords for the NES, because generally speaking you can only play 3 notes at a time. And you’d probably want the different channels doing something more interesting than working together to combine one simultaneous chord.

Since that rules out a practical use for conventional chords, the arpeggio effect works by using fast, broken chords. Instead of playing the notes “D F A” at the same time, you can have one channel alternate rapidly between those notes, kind of like how a classic telephone ring sounds. 

This was particularly present in C64 music, because it only had three channels (versus the NES’ 5, although it was much more versatile in other ways…). Cramming as much as you could into one channel was important on the C64, and that helped give birth to a style of vgm that drips with arps. [Example - Myth C64, by Jeroen Tel]

Anyways, I opened up the M.C. Kids Level 4 track and examined the first arpeggio:

MC Kids Arp, Volume Envelope

^This is the volume envelope. There’s nothing particularly special or C64-like about it. It has a little volume bump instead of having an uninterrupted fade, which adds some detail to the sound.

MC Kids Arp, Arpeggio

^This is the arpeggio table/envelope, responsible for bringing the C64-ness.

The frame rate of the NTSC NES/Famicom is 60fps, which is the standard resolution at which you can manipulate sounds. Anything can change that fast on the NES, including pitch, which is what allows these fast arpeggios. On the bar graph above, every bar lasts 1/60th of a second (revealing that each note lasts 2/60ths). The first two bars are the root note of the chord, then each available space represents the nearest half-step on a keyboard. So it jumps up 4 half steps, then 3 more (7 from the original note). If you’re musically inclined, this particular arpeggio effect is creating a major triad.

MC Kids, Duty

^And lastly, there is a looped modulating set of duty cycles, which contributes to the voice sounding Western (it’s not uncommon for Japanese soundtracks to use changing duty cycles, but they usually don’t loop constantly).

If you’ve watched the introduction to the NES sound channels video below, you saw a quick explanation of the different “instruments” that the pulse wave channels can be. There’s 12.5%, 25%, 50%, and 75%. The graph doesn’t make it clear, but that’s the Y-axis here. 0 = you’re using the 12.5% voice, 1 = 25%, etc.

Another way to think of it- as the note sustains, it is “changing instruments” repeatedly.

For the famitracker/ MML-using readers, here’s the instrument data:

  • Volume: 0 8 6 6 5 4 4 4 4 4 4 4 4 4 3 2 3 4 4 4 4 4 3 3 3 3 3 2 2 2 2 2 0 
  • Arpeggio: | 0 0 4 4 7 7 
  • Duty Cycle: 2 2 2 2 2 2 2 | 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 2 2 2 2 2 2

I hope that wasn’t a needlessly long response, but this was the perfect opportunity to elaborate on a couple concepts. MC Kids also does neat stuff like triangle channel kick drums, but that’s a topic for a future post.

I’ll close with my favorite track from MC Kids. :)