CHIPTUNES
,are in my eyes, an artform. Not a genre. And people who say otherwise are WRONG. Chiptunes are compositions made with 80s or 90s soundchips from computers from the time. There is also something called "Fakebit". Fakebit is making music that sounds like its using soundchips from the 80s or 90s but isnt really. You can usually sniff it out by the kinds of waves (example, 4 squares waves and 2 triangles. No computer existed back then that had that, so its probably fakebit) or the ammount of channels (example, 267).
The NES/Famicon for example had 5 sound channels; 2 Squares, a Triangle, a Noise, and a DPCM (sample). This might not seem like a lot, which is the whole point. The whole point of why people (or atleast I) use these old soundchips is because of how limiting it is. It's so limiting, it FORCES you to think outside the box.
I will be talking about the cool things the Richo A203 (NES/Famicon soundchip) could do. If you're interested the soundchips of other computers, like the gameboy or Commodore 64, then idfk, look up stuff in the internet.
CHANNELS
As previously mentioned, the A203 has 5 soundchannels, which means 5 sounds can play at the same time. That is also why when you do anything that triggers a sound effects (for example, jumping or getting a coin) in Super Mario Bros., the melody cuts out temporarily. I also purposely made the 5 channels sound very weak earlier. But they are actually really strong, and can make beautiful sounds. You just need to know what they're capable of. Btw, under the title of each bit I have written the registers. The registers are used for coding. I only wrote the part of the code you need to write to turn the waveform on
SQUARES
[Square 01 $4000–$4003][Square 02 $4004–$4007]
Square 01 is usally used for the melody, while square 02 is used for varios things. The square waves have 4 types of duty cycles, which 3 make different sounds. The duty cycles are 12.5%, 25%, 50% and 75%. 25% and 75% make the same sound. But this can be used for interesting effects. In Gremlins 2, there is a plucky effect by changing the duty cycle from 50% to 25% in a franction of a second. While in Alien 3, the duty cycle changes from 25% to 12.5%, except way slower, to make a vocal effect.
Enough about duty cycles, now on to arpeggios. An arpeggio is playing the notes of a chord one after another instead of at the same time. When referring to arpeggios in chiptunes, the notes of the arpeggio change every frame (which js really fast). So fast in fact, it sounds like its playing at the same time.
You can also make an echo/ reverb effect, using either 1 or both audio channel. When using both, you can copy the melody, move it a little forward and make it quiter, you get an echo/reverb effect. But if you want to create an echo with one channel, you can do it like this. Picture you have a normal slow arpeggio in your song that goes like: [C-E-F-C][C-E-F-C]. If you know put a quiter note after each note, you get an echo effect like. But if you want a bigger and better, you can make something like this: [C-c-E-c-F-e-C-f][C-c-E-c-F-e-C-f].
TRIANGLE
[$4008–$400B]
The triangle wave is usually used as a bass. It only has one duty cycle. Also something really notible, is that its not a real triangle wave. It is very lumpy and ragged, which is what gives it its iconic sound. But its not only used as a bass. It can also a drum kick. This can be achieved by making a short E4 or C4 note and sliding it down as much as possible.
NOISE
[$400C–$400F]
The noise channel is usually used as percussion. The channel has 2 duty cycles. One duty cycle makes a TV static like sound, which is heard in most songs. The other duty cycle makes a more metalic, sometimes melodic sound, which is used in Metal Crusher from Undertale. It can be used to make a cymbal (long A#3 with decay), hi-hat (short A#3) or snare(G#3 or G3 with decay) like sound.
DPCM
[$4010–$4013]
The DPCM channel, which stands for Delta Pulse Code Modulation, can play a sample, which is a prerecorded sound. The only thing is that they are usually low quality (1-bit), mono and have a max length of 2 seconds. DPCM samples usally sound muffled and a little grainy. but there are can examples where DPCM samples sound almost 4-bit (SNES like), like in, of all things, Big Bird's Hide And Speak.
The DPCM channel is usually used for drums, in for example Super Mario Bros. 3, but it can also be used for melodic instruments, seeing as the pitch can be changed. It wasn't all the common however. For one, although the pitch can be changed, it can only be lowerd. And by changing the pitch, you also change the speed of the sample, making lower notes sound distorted. Furthermore, there are 16 possible pitches, 15 not counting the original sampel's pitch.
You would assume that you could just lower a C to a B and an A# and an A# and so forth. But you would be mistaken, seeing as there are gaps that prevent this, which all are a different size. If you had a sample of a note playing C4 (Ocatve 4), you will be able to pitch it to the following tones: [C4-G3-E3-C3-A2-G2-F2-D2-C2-B1-A1-G1-F1-E1-D1-C1].
But this didn't stop Sunsoft however. They famousily used the DPCM channel for a funky bass in their games. It can be heard in the Title Theme to Journey To Sillius. Sunsoft used 5 samples: A#, B, C, C# and D. All the samples together are 1KB, which at the time was a lot. Although most Sunsoft games used the same bass sample, Fester's Quest used a different one, and some orchestra hits.
Sunsoft Bass (B) sample as a waveform.
Rob hubbard used the DPCM channel to generate a saw wave. He did this by adding a short sample of a saw wave, and making that loop. It is only 17 bytes, and he only had to add one note. It is used as a low, buzzing bass sound. You could theoratically use this same technique, except for other waveforms.
Saw wave sample as a waveform.
EXPANSIONS
No, not like the ones on Deviantart. When talking about the A203, expansions refer to soundchips that are added from the catridge instead of the systems soundchip. Nintendo publised a lot of catridges using soundchips, mostly the FDS, but never out of Japan. However, other companies like Sunsoft, Namco and Konami did actually make catridges with soundchips outside of Japan
VRC6
[Square 01 $9000][Square 02 $A000][Saw $B000]
Fools_In_April
The VRC6 expansion, which stands for the Virtual ROM Controller 6, is a soundchip made by Konami in 1989. It adds 3 channels; two square waves and a saw wave. It is the only expansion to ever add a saw wave.
The square waves have 8 duty cycles. Those being: 6.25%, 12.5%, 18.75%, 25%, 31.25%, 37.5%, 43.75%, 50%. This means that they can make 5 more sounds then the NES!'s squares.
The saw wave is very comparible to the triangle wave. They are both used as a bass, have 1 duty cycle and aren't the true versions of what they're supposed to be. The VRC6's saw is ragged which makes it a little muffled, just like the triangle. The only thing they don't have in common is that you can't use the saw as a kick (or I wouldn't recomend it).
Although the VRC6 is used in a lot of modern chiptunes, it was barely actually used back in the day. Only three games used it, that being: Akumajou Densetsu, Esper Dream 2 and Madara.
Sunsoft 5B
[Square A $00-$01][Square B $02-$03][Square C $04-$05][Noise $06-$07][Envelope $08-$0F]
Battle_Against_An_Evil_Printer
The Sunsoft 5B is a soundchip made by Sunsoft in 1990. It was only ever used in their game Gimmick!/Mr. Gimmick. The audio hardware is a type of Yamaha YM2149F, which is a variant of the General Instrument AY-3-8910 PSG. The AY-3-8910 is a 3-voice Programmable Sound Generator (PSG) that was made by Genral Insrument in 1978. The Sunsoft 5B is variant of it, thats why I brought it up
The Sunsoft 5B adds 3 channels. They are all square waves, but can switch to noise channels, envelope and Square and noise at the sametime. The noise generator produces a 1-bit random output with a period controlled by the CPU clock and the 5-bit period value in register $06. That is what makes it sound different from the A203 noise channel.
Nintendo FDS
[$4023-$4097]
Keygen
The Nintendo FDS, which stands for Famicon Disk System, is a soundchip made by Nintendo in 1986. It adds 1 channel, has a wavetable synthesizer, which you can make custom waveforms with. The FDS has a 64-step wavetable where each step is a 7-bit value from 0 to 63. The chip continuously loops through these values at a programmable speed to create sound. I have also had the thought that you might be able to could play 2-bit samples with it. But if you wanted to do that, you'd have to convert your audio file to a 64-step waveform.
There are a lot of games that use the FDS; 75 in fact. I won't bother listing up them all, but I will tell you some I found that peaked my interest
Apple Town Monogatari – Little Computer People, Bishoujo Sexy Derby, Deep Dungeon 2 – Yuushi no Monshou, Doki Doki Panic, Egger Land, Family Composer, I am a Teacher – Super Mario no Sweater, Idol Hotline – Nakayama Miho no Tokimeki High School, Kaettekita Mario Bros., Sexy Invaders and Super Mario Bros. 2.
Namco 163
[Channel 1 $40-$47][Channel 2 $48-$4F][Channel 3 $50-$57][Channel 4 $58-$5F][Channel 5 $60-$67][Channel 6 $68-$6F][Channel 7 $70-$77][Channel 8 $78-7F]
8_THOUSAND_MARCH