The ZX Spectrum is a home computer developed by UK-based Sinclair Research and released on April 21, 1982. At the time of its debut, it was an impressive computer, but four months later, the Commodore 64 was released making the Spectrum look outdated. Despite being technically out-classed, the low cost of the ZX Spectrum allowed for massive sales and widespread use throughout the UK and Europe. It was especially popular in Spain and USSR/CIS countries. Software was originally loaded using cassette tapes, but later models featured disk drives.
Although various models were released over the years, each with upgrades to the hardware, most Spectrum software is compatible with the original Spectrum 48K model.
ZX Spectrum 16K/48K
Upon it's first release, the ZX Spectrum could be bought with 16K of on-board RAM, or 48K. This model featured a poorly-made rubber keyboard. Display went to a television, and audio consisted merely of a PC Speaker.
This model, released in 1984, was essentially a Spectrum 48K with a new case and better keyboard. It still uses a PC Speaker for audio.
ZX Spectrum 128K
The 128 model was released in 1985 and comes with 128 KB RAM, an RS-232 serial port, an RGB monitor port, and 32 KB of ROM including an improved BASIC editor. Most important to this site, the 128 features a proper audio chip, a three-channel AY-3-8912 and MIDI compatibility.
ZX Spectrum +2
ZX Spectrum +2A
ZX Spectrum +3
ZX Spectrum +2B/+3B
Due to the popularity of the ZX Spectrum, and the loyalty of fans, tens of thousands of games were released for the platform.
Music and Sound
The first couple models of the ZX Spectrum featured a PC Speaker known as a buzzer. The Spectrum ROM has a BEEP command which can play a square wave in 10 octaves and can be called from both BASIC and machine code. When using the buzzer directly, programmers have to write 1-bit sample data. Many of them simply used bits of the Spectrum ROM as noisy sound effects or percussion. Some knew how to do pulse width modulation or mix several voices together. They were able to push the buzzer to the limit and, by devoting most of the CPU to audio, were able to play very impressive sounding tunes.