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| A field guide to chipmusic |
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Chipmusic is simple non-sampled computer music, usually generated by a
sound chip with a few simple oscillators on it. You may also hear it
referred to as chiptunes, intro-music, or keygen music, depending on
who you ask.
Chip musicians have spread throughout the world, but most are still
found in the largest home computer markets of the 1980s: Europe, East
Asia, and North America. Many chip musicians are involved in the
demoscene, and convene on the Internet to share their latest works and
compete in song-writing competitions ("compos"), tests of musical
talent and technological skill!
For these reasons, you will find chipmusic scattered all around the
Internet, and it's a particularly good match for the small Internet
and the fediverse. This page is a field guide to the most common
chipmusic platforms. It will help you identify the most common
computers of the 1980s and 1990s just by listening to the sounds they
make.
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| Commodore 64 [1982] |
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(BIN) Example: Fanta - Lame Over
The C64's SID chip sounds like a simple analog synth, with massive
basslines and arpeggios but limited polyphony. When unfiltered,
it is buzzy and metallic.
Unlike its contemporaries, the SID was a full-featured
synth-on-a-chip: it can generate not only rectangle waves, but
also tri, saw, and noise, and modify the above with a sweepable
analog filter. Admittedly, the SID is fiddly -- songs written for
one hardware revision break on another, and the analog filter is
notoriously hard to emulate (to say nothing of the various hardware
bugs that are exploited in well-crafted songs). Still, it was the
premier demoscene platform of its day, and remains one of the most
capable and widely used chipmusic platforms.
The SID has three channels. Any waveform (rec/square, saw, noise)
can be used in any channel, at any time. Automatic pulse-width
sweeps are available: ring modulation and sync are also allowed.
Each channel has an amplitude ADSR and can be piped into a single
resonant filter (hi/lo/band-pass), which can be swept while the
notes are playing.
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| Commodore Amiga [1985] |
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(BIN) Example: Tempest - Acidjazzed Evening
The Amiga packed an innovative four-channel sampler known as
Paula. It could faithfully reproduce far more than chipmusic, but
this remained common because of its modest space requirements and
growing acceptance as an art form.
Some songs were written to be reminiscent of older platforms, like
the C64. Others used the Amiga's extra CPU power to simulate extra
channels (by "mapping" several software-mixed channels onto each
of Paula's four hardware channels).
Paula is distinctive for having two of its channels panned hard-left
and the other two hard-right, to the consternation of headphone
users.
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| Atari ST [1985] |
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(BIN) Example: Tao - Da Chipshit
The ST's YM2149 has been variously described as "tinny", "cheese
grater", and "those frequencies just about ripped my ear off".
Released in 1985, the Atari ST was a powerful machine indeed. It
was among the first 32-bit home computers, and included all sorts
of futuristic features -- a proper GUI, a mouse, and even built-in
MIDI support. Given all this, its audio hardware was weirdly
anachronistic: three channels of square waves or white noise. But
what the YM chip lacks in range, it makes up for in hackability.
Relatively simple timing tricks can expand the chip's capabilities,
"faking" new waveforms as well as producing seriously evil noises.
The YM2149's great strength is its simplicity. It is essentially
a state machine, so it can be emulated precisely, or grokked in
fullness.
A lot of other machines used the YM2149 or its sister-chip the
AY-3-8910. These more or less share the ST's audio capabilities,
although most lacked the CPU power required to pull off certain
tricks the ST is famous for.
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| Atari 8-bit (400/800/XL/XE) [1979] |
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(BIN) Example: Adam Bienias - Bitter Reality
The Atari's POKEY chip has true four-channel polyphony and a broad
timbral range. It also has many quirks and limitations, among them
minor detuning* and an inaccurately named high-pass filter**.
The Atari 8-bit family used the POKEY soundchip until 1992, amazing
for a chip first produced in the late 70s. It's one of the few sound
chips that really *did* have four usable tonal channels (at
least in some configurations), a capability that has been put to
good use over the years.
POKEY has four channels, any of which can output a pulse wave
or noise. Each channel has adjustable volume (0-15). Two simple
digital high-pass filters** are available and can be enabled on
the first two channels only.
* Trivia: The tuning problems arise because frequency must be
specified with a single 8-bit value (0-255) corresponding to equally
separated "steps". This doesn't coexist nicely with the chromatic
scale. It is possible to combine two channels into one and specify
its frequency with a single 16-bit value (0-65535); the resulting
(single) channel will be properly tuned, but at a cost to polyphony.
It is also possible to adjust the duty cycle of the doubled channel
through timing tricks.
** More trivia: The so-called "high-pass" filter is not quite that,
but more of an edge detector; it outputs a short pulse every
time the input square wave transitions from LOW to HIGH or vice
versa. This explains some of POKEY's more unusual sounds.
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| Nintendo Entertainment System [1983] |
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(BIN) Example: Konami - Contra [theme]
The NES is bassy and powerful, with a hint of bit-crushing thanks
to cheap DACs. Its CPU (a 6502-derivative, the Ricoh 2A03) also
served as its soundchip.
The NES was not the first popular game console, but it was the first
to take music seriously. Its 2A03 had enough tonal channels (3) to
allow full chords to be played without interrupting the percussion,
a feature that shaped the evolution of Japanese chipmusic. It even
had crude support for sample playback (although the feature was
clearly intended for percussion instruments and was not used much).
Each of the 2A03's channels has different capabilities:
- 1. pulse (selectable duty cycle, volume envelope, freq. sweep)
- 2. pulse (selectable duty cycle, volume envelope, freq. sweep)
- 3. triangle (no volume control)
- 4. noise (selectable noise type, volume envelope)
- 5. sample (limited repitching capabilities)
(Yes, the NES has 5-note polyphony; amazing!)
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| Nintendo GameBoy [1989] |
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(BIN) Example: Snorpung - Gejmboj
The Gameboy is pleasantly crunchy with a hint of ear-bleeding
waveforms. Like the NES, its CPU (a Z80-derivative, the Sharp
LR35902) also serves as its soundchip.
The Gameboy's real influence arose from its ubiquity and portability;
it is not just a good platform for audio, but also a battle-hardened
plastic brick that you can carry anywhere. It's not surprising
that the idea of "touring chipmusic acts" is so common in the
Gameboy scene. The unit's modularity also makes it convenient to
incorporate into one's DAW setup.
Thanks to such titles as Tetris and Pokemon, Gameboys are everywhere,
and thanks to years of development they have become a mature platform
that is documented and understood fully.
The Gameboy was clearly patterned after the NES, but featured a
slightly different set of channels. Most notably, the triangle and
sample channels were merged into a single configurable WAV channel
(which served as a primitive sampler). Consequently, it had a
broader tonal range than the NES, but slightly less polyphony.
Each of the Gameboy's channels has different capabilities:
- 1. pulse (selectable duty cycle, volume envelope, frequency sweep)
- 2. pulse (selectable duty cycle, volume envelope)
- 3. wave (programmable 4-bit waveform, 4-level volume control)
- 4. noise (selectable noise type, volume envelope)
The same audio hardware was reused unchanged in the Gameboy Color,
and has been included for backwards compatibility in every GB
manufactured since!
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