A question about musical technology

Anonus

You know how in, like, Flying Battery Zone Act 2, you can get part of the music to drop out if you get a sound effect (like a spring noise) to play? How does that happen?

(It's not just old-school games; you can get part of the music for Techno Base Act 2 in Sonic Advance 2 to drop out too)

Salix Babylonika

I am not sure of the specific thing being referenced, but that's often not actually deliberate.

Early game consoles had pretty limited sound hardware, if there were too many sounds playing at once, some would drop out because the system couldn't process them all simultaneously.

But! I am not an expert on VGM, someone with more knowledge can maybe provide a more thorough answer.

Anonus

I know it's not deliberate, I'm just wondering how it works, because nobody seems to really separate chiptunes into "layers" on purpose and, like, put those layers on YouTube.

Salix Babylonika

it's very difficult--nearing impossible--to re-seperate music into layers after it's been mixed.

Anonus

well

I think a lot of the 30-minute loops on YouTube are the result of ripping the chiptunes directly from games, where they wouldn't be "mixed"

Sredni Vashtar

Yeah, magically separating sounds from other sounds is semi-possible if you focus on the spectrum of an individual element of the piece and filter the rest out, but even then the shadow of anything else in that frequency range is still going to be imprinted there and it's very hard to remove. With chiptunes, the individual sounds are basically the same sounds, sooooo... yeah, even with super technology, you probably need the individual tracks.

Anonus

so it would be like when people separate MLP:FIM's background music out and you can still faintly hear the dialogue/sound effects?

Anonus

(Nobody seems to do this for any other show's BGM!)

Sredni Vashtar

Yes. People also do this to songs when they do mashups if they cannot find the stem files. It's a common trick.

Klinotaxis

ok, so this is Sonic & Knuckles, yes? let's say on on the Genesis.

the genesis actually has two sound chips, a Yamaha YM2612 and a TI SN76489. the YM2612 has six monophone FM synths, an LFO, some other junk. the SN76489 has three square waves and one noise. both sound chips were controlled by the CPU through a subprocessor, a Z80.

you can see multiple bottlenecks that could result in the effect you're describing. e.g., the CPU-Z80 bridge could be simple and not allow full use of both sound chips simultaneously, or the full capabilities of both sound chips would be required together to play the soundtrack.

chiptunes aren't separated into "layers" because the sound is not produced in the manner of traditional music, with a score, or a modern recording, a linear series of samples. each chiptune is effectively a subprogram of the game, a computable object. so this separation sort of thing is hard to manage.

(chiptunes of course usually have traditional scores/tunes - i'm just saying this is not how the hardware works)

Klinotaxis

GBA does have sample-based synthesis, but mixing sounds might be a pain (can't just add samples, you have to scale them so it's not twice as loud, that sorta shit)

has a Z80 for backwards compat (for several things, including sound). lol

Anonus

so it's not possible to, like, deliberately block out the "twang" sounds in Flying Battery Act 2's music by design?

Klinotaxis

more like they didn't bother with separate volume controls for sfx and music, either because of technical constraints or apathy. which is pretty much what everyone else said. but in addition, the bgm probably doesn't exist in the game ROM, so it can't be extracted that way except by reverse engineering with a good understanding of how the particular game put sounds together.

Klinotaxis

a game with actual chiptunes isn't like a CD, I mean. the music doesn't exist as a rippable unit

Anonus

how would an emulator handle it?

Klinotaxis

depends. more than one way to write an emulator.

if it was me, i'd try to emulate the coprocessor and the sound chips, except with the sound chips playing recorded square waves/whatever on the PC. should sound identical that way, if the emulation's good. this is the "low-level" approach preferred by e.g. Higan. it also doesn't make "ripping" "tracks" any easier than it would be on an actual Genesis.

you could also take a "high-level" approach, like any N64 emulator not written by Nintendo. maybe slightly harder to explain but amounts to writing your own sound generator that tries to react to the emulated CPU commands appropriately. could be as "high-level" as special-casing the Sonic & Knuckles ROM to play various recordings (possibly with the "twang") at various times.

dolphin has both available, you can compare & contrast https://wiki.dolphin-emu.org/index.php?title=DSP_LLE

glennmagusharvey

I am not sure of the technical details being discussed here, but here's what I know.

I am less familiar with Genesis hardware, but I know that the NES (and Game Boy) had only very limited numbers of sound channels, and very often things like the Mega Man games would pipe sound effects through one of the sound channels, despite that channel also carrying music data.

I think NES and GB both have 3 channels for pitched sound and 1 channel for noise. SNES has 8 channels, and more flexibility in what those channels can be used for instrument-wise.

So when a sound effect comes through, that channel would temporarily stop playing music and only play the sound effect, then resume playing the music when the effect has ended.

Some games got around this creatively. For example, the GB Pokémon games have very few percussion effects, which means the noise channel is free for sound effects to use most of the time.

If you download videogame music in machine (or one could say, emulator) formats -- that is, NSF, SPC, GSF, etc. -- you can frequently use the player or plugin that plays them to mute one or more tracks. For example, you can mute the wind effects in the Death Mountain theme of Link to the Past.

This music is ripped from the game by people basically figuring out how the sound data is compressed into the rom data and extracting it, and also figuring out how the game system handled sound data and writing a program or media player plugin that duplicated that functionality.

GBA specifically expanded on GB's sound hardware by featuring both GB's chiptune sound channels and a more advanced channel (or channels) that could play a far wider variety of stuff, but in a way that I don't think can be taken apart. You have some games that make use of both, such as the soundtracks to Castlevania: Aria of Sorrow and (infamously) Harmony of Dissonance.

lee4hmz

On machines with PSGs like the AY-3-8910 or the SN76496/76489, you had something like three voices plus noise, and if a sound effect and the music both needed a channel at the same time, usually the sound effect would win out. The NES is similar, though I think it had one or two more channels.

You don't see a lot of this channel-stealing behaviour on newer stuff simply because there's more of them to go around. The SNES, as noted, had 8, the PlayStation had either 24 or 32 (I forget), and modern software mixing can handle as many as your CPU can stand.

glennmagusharvey

Or it can simply play an audio recording stream rather than having to emulate a set of instruments one by one.

lee4hmz

Yup...I remember the CD version of WarCraft 2 doing that with CD-DA tracks on the disc (back when CD-ROM drives had actual patch cables to the sound card instead of extracting the tracks over ATAPI).

Section42L

Anonus said:

so it would be like when people separate MLP:FIM's background music out and you can still faintly hear the dialogue/sound effects?

We should be thankful that the people who do the background music for Steven Universe have released the separated tracks on Soundcloud for everybody to listen to.

Anonus

I wish Pat Irwin would release more than just that one track of Rocko's Modern Life BGM...

Anonus

Also, among other things, I am eternally grateful to Fred Seibert for uploading the Hanna-Barbera's Pic-A-Nic Basket of Cartoon Classics album

Imipolex G

I'm late to the party here, but the Fusion emulator can be set to only play some of those sound channels and not others. I used this the other day to isolate some chords on a track I was curious about. Haven't tried it on a Sonic game, though

Imipolex G

actually, no, I lied. It's the Gens emulator that can do this