1-bit music for Atari, C64, and MSX
26 03 11 - 23:42In 1980s 1-bit music was used on computers such as Apple II, ZX Spectrum, or IBM PC, just because there was no other choice - all the audio capabilities these computers had by default were limited to a simple speaker controlled by an output pin of a port (a bit more complex for IBM PC). Additional sound devices for these computers, although existed, weren't widespread. Other computers of the time had sound chips, so you probably won't find 1-bit or other software-synthesized music on them.
Nowadays, however, 1-bit music could be considered not just as a technical limitation, but also as a stylistic choice, a way to produce different, unusual sound. Technicaly it could be done, to some extent, on almost any computer with some kind of sound or tape output. Some computers have additional 1-bit sound output used for system things like keyboard click or start-up beeps. If no such an special output available, sound chip could be used as 1-bit output device, by setting it to a state where it does not generate sound, and writes into a volume register changes output level directly (basically a simple DAC).
In 2000s some 1-bit music was actually played on few 8-bit computers which has sound chips by default. Here is short overview of these programs.
Atari XL/XE
This computer has POKEY sound chip as main sound device, but it's video controller, CTIA, has four bits of output port, and one of these bits was used to produce sound of keyboard click. It was connected to a speaker in early models, and mixed with POKEY sound it later models.
XXL, a Poland coder and Atari enthusiast, made a great work in 2008-2009 for 1-bit Atari music. He ported a lot of music engines from ZX Spectrum, which is really difficult task, because ZX Spectrum has Z80 CPU, and Atari has 6502 CPU - these are very different, and 1-bit music engines usually push a CPU to it's limits and rely on it's timings really heavily. Also, source code of these engines wasn't available, they had to be reverse-engineered first. Ported engines allowed to play some ZX Spectrum music of both classic and modern authors on Atari.
Not every Atari emulator capable to emulate CTIA sound properly. Latest version of Altirra works good.
Beep'em All
A first Atari 1-bit music compilation made in 2008. It contains six songs of modern authors - five songs by Mister Beep, and one by Factor6. All the songs use ported Music Studio engine. This program allows to choose sound output device - CTIA or POKEY. POKEY does not generate sound by itself in this case, is used as an output port.
Beep'em All II
A music compilation made in 2009. It is considerably larger than the first one, it has 19 songs, both modern and from games of 1980s. The songs are using a lot of different ported engines - ZX-7, Music Synth, Music Studio, Tim Follin's three channel, Lyndon Sharp's, and a few others.
Isora
A logic game made in 2009. Before the game starts, it plays 1-bit music by Mister Beep. It uses ported Music Studio engine. The game itself has usual POKEY music made by other author.
Commodore 64
This computer has the famous SID sound chip. No other sound output available, so only SID could be used as output device.
In 2010 512Beepology, an 512 bytes intro for Commodore 64 with 1-bit music, was released. It just plays music with a black screen. It uses Music Studio engine ported by XXL, and Factor6's music.
You need to turn on resampling option in a Commodore 64 emulator in order to get proper sound.
MSX
This computer has AY-3-8910 or compatible sound chip. In addition, one line of a system I/O port used as sound output to generate sound of keyboard click.
In 2006 Dioniso, a MSX coder from Spain, made Beepertron, a game for MSXDev compo. It is a sound memory game with 1-bit sound, you have to listen, memorize and play music phrases generated by computer. It also has title music made by the author of the game. This game has original sound engine with one channel of tone and drums. The engine capable to produce unusual sounds and sort of chords.
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