GSC Sound Engine Part 4 - The Noise Channel

If the Pulse channels are your bog-standard, classic, and reliable instruments, and the Wave channel adds in the spice to make the GameBoy sound distinctive, then the Noise channel is that funky uncle that doesn't quite fit with the others.

Unlike the Pulse and Wave channels, the Noise channel doesn't actually make any sounds that can be called a "note"; instead, it produces pseudo-random noise that sounds something like like old television static. Instead of traditional notes, each of these "noise notes" have a certain frequency, so some sound like "soft" static and others like or "harsh" static. If you want a random example of how the noise channel sounds, check out this video (this is for the NES but the noise channel on the GB is identical to the NES')

To help guide this explanation, I highly encourage you download and play around with this little GB program called NoiseTest, which shows off the various notes of the Noise channel (please trust the link, I can't find it online anywhere!). Any GameBoy emulator should be able to run this, but if you need a recommendation, the one I used is called bgb.

https://drive.google.com/file/d/1psp2i2HUzr1hvsCx2ba0xC5x5eS_JJRg

Even if you can't download and use this little program, don't worry. I'll try to make the explanation understandable with other audio links.

Here's a view of the application and it'll guide us through how the noise notes are produced. The number column on the left and the row on the bottom combine to produce the index of the noise note on the top-right (the $XX). Note that there's actually a mistake in this program and the second half of the row of numbers should actually be "8-9-A-B-C-D-E-F", continuing in hexadecimal from the rest of the row.

Each of these little squares represents one of the possible "noise notes". The further down and right you go, the lower the pitch of the note, with the downward adjustments being more significant than rightward adjustments. No need to count them all - there are 256 squares and thus 256 possible noise notes! But the majority are either usable or not useful.

You might notice that there are two columns of squares, the "long" column on the left and the "short" column on the right. Without getting into boring technical details, this is referring to the base frequency of the noise notes. The noise notes on the "short" column have a shorter frequency, so they sound much higher pitched compared to the "long" notes. This column is basically only useful for making Triangle or bell-like sounds, which have very limited used, so let's ignore it for now.

So about the left column - 128 noise notes are a lot to choose from, right? Well, actually, almost half of them (anything below the 8) are unusable for actual music. This is because they are so low-pitched you can barely hear them. So we're left with around 64 noise notes. Showing them all off would be boring and take a while, so instead, I'm gonna show you just the leftmost column, or what you can consider to be the first member of a "family" of notes:

https://on.soundcloud.com/a15R6

You can think of the notes to the right of each of these as tiny "adjustments" that lower the pitch a bit each time. The notes sound very similar to one another at points (for example, $01 and $10 sound the same), so there's not actually 64 distinct sounds.

There's another couple of layers of customization possible besides the base frequency of the notes:

• The first is obviously the volume. It works much like the Pulse channels, with 15 possible volume numbers.

• The second is the envelope of the notes, or how they fade out and fade in (this is also the same as with the Pulse channels). In the case of the noise notes, only fade-out is possible. There's 7 levels of fade-out, but usually, the envelope is kept close to the minimum amount (1 to 3 of 7) on noise notes. In the example above, I used a fade out of 2.

Ok, so this is all very interesting (I hope), but what about the GSC sound engine? How does it use the noise channel?

Well, much like the Wave channel, there are preset noise "notes" backed in the engine! 36 of them, in fact! However, there are a lot of repetitions, unused sounds (some are relics from the RBY sound engine), sounds that are basically silence, and some sounds are so similar you cannot really distinguish them, so the real number is closer to 20 or so. The guys at pokecrystal labeled them with useful names that arc back to real-life instruments like Snares, Drums, Hi-hats, Kicks, and Crashes (obviously, in the code of the game itself they have no names and we don't know what the developers called them either).

Here are roughly where the GSC sound engine's preset sounds are located. The blues are "Drums", the greens are "Hi-hats", the reds "Snares" and the yellows "Triangles". There's a few overlaps between categories here and there, and often the difference between different noise notes is the volume or the envelope of the note itself.

If you paid attention, you might notice that there are a couple of categories missing: the Kicks and the Crashes. With the crashes, they are actually just $12 with a long envelope so I decided to not include it in the picture. With the Kicks (actually, there's two of them but they sound identical), the GSC sound engine does something very clever: they combine different noise notes to make one big note! This is especially useful with the Kicks: you get the deep sound first, but the note is cut before it gets to the ugly twangy part after. Here, take a listen:

https://on.soundcloud.com/JgMLD

The first is just one note ($6B), and the second cuts off the sound and finishes it with a little bit of index $00. Doesn't the second one sound much better? I actually use this technique for kicks in my non-Pokémon demixes! There are other noise notes that use this "double note" technique, but the kick is the one I use the most by far.

Finally, there's another annoying aspect about the GSC sound engine I wanna talk about: the drumkits. You see, natively, you can't actually just pick and choose which noise note you want to use. You need to define one of 6 drumkits for your song, and each drumkit contains only 12 notes (labeled from C_ to B_, used like if they were a full scale of notes). This means that an important step in arranging a song for the GSC sound engine is to pick which drumkit fits the song the best.

• I believe Drumkit $0 is the same and only drumkit used in RBY. It contains a lot of strong Snares whose only difference is volume, a couple of Hi-hats and Triangles. It also contains a relic of the RBY engine, Drum05, which is a "combo note" that rises in pitch, and is used in the Title Screen theme. You can hear it here: https://youtu.be/njoPUWILwpo?t=56

• Drumkit $1 is a jack-of-all-trades. It has a few strong Snares, but also softer Snares, Hi-hats and Triangles.

• Drumkit $2 is actually unused! It's basically identical to $0, just changing the volume of some notes.

• Drumkit $3 is where things get interesting. What it lacks in volume variation in strong Snares it makes up for being the first drumkit to have a Kick and a Crash. Sadly, it only contains one Triangle and one Hi-hat, which makes it rather limited sometimes. To add insult to injury, it has a couple of "holes" in it (noise notes that are so low they are basically unused). If only it had a couple extra sounds, it would literally be perfect...

• Drumkit $4 is very similar to $3, except it doesn't contain a Hi Hat. So I basically never use it.

• Drumkit $5 is also very similar to $3, but it contains no holes, so it's much more useful when approaching a generic song. Definitely the one I use the most.

And that's basically it! I skipped over a couple of aspects, but hopefully you'll now pay more attention to this often-forgotten channel that can add a lot to a song.