Casio CZ-101

The CZ series is a family of low-cost phase distortion synthesizers produced by Casio in the mid-1980s. Eight models of CZ synthesizers were released: the CZ-101, CZ-230S, CZ-1000, CZ-2000S, CZ-2600S, CZ-3000, CZ-5000, and the CZ-1. Additionally, the home-keyboard model CT-6500 used 48 phase distortion presets from the CZ line. The CZ synthesizers' price at the time of their introduction made programmable synthesizers affordable enough to be purchased by garage bands. Yamaha soon introduced their own low-cost digital synthesizers, including the DX-21 and DX-100, in light of the CZ series' success.

Casio's phase distortion synthesis technique was championed by Casio engineer Mark Fukuda and evolved from the Cosmo Synth System that was custom-developed for legendary synthesist-composer Isao Tomita. Yukihiro Takahashi was also on board during development; he then toured with a CZ-1 in 1986. To make the CZ synthesizers inexpensive, so they would be affordable to amateur musicians (a much larger market than the professional musician market), Casio used digital synthesis without a filter instead of traditional analog subtractive synthesis with a filter. Like many early digital synthesizers, its sound was regarded as "thinner" than the sound of an analog synthesizer. However, the CZ line used phase distortion to simulate an analog filter. It had in total eight different waveforms: as well as the standard sawtooth, square, and pulse waveforms, it had a special double sine waveform, a half-sine waveform, and three waveforms with simulated filter resonance: resonant sawtooth, triangle, and trapezoidal waveforms. The simulated filter resonance was not considered to sound much like real filter resonance, being a simple waveform at the filter cutoff value instead of a real filter resonating.

Each digital oscillator could have one or two waveforms. Unlike other synthesizers, where having multiple waveforms caused those multiple waveforms to be mixed together (parallel), the CZ synthesizers would play one waveform and then play the other, and so on in alternation (series). This could cause the appearance of a sub-harmonic one octave below the nominal pitch of the sound, due to the period of the combined waveform taking twice as long as a single waveform would. It was possible to combine two non-resonant waveforms together, and to combine a resonant waveform with a non-resonant waveform, but it was not possible to combine two resonant waveforms.

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