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 (1985) and Yamaha DX100, in light of the CZ series' success.
Programming
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.
Digital Controlled Oscillator (DCO) The CZ-101 and CZ-1000 have eight digital oscillators, each with a dedicated 8-stage pitch envelope. For patches using one oscillator per voice, this allows 8-note polyphony, If two oscillators per voice are used, the polyphony is limited to four voices. The CZ-3000, CZ-5000, and CZ-1 had sixteen digital oscillators, making them sixteen- or eight-voice synthesizers. Each of the oscillators in a two-oscillator patch could be independently programmed.
Digital Controlled Wave (DCW) The DCW adjusts the magnitude of phase distortion that is applied to the oscillator. For non-resonant wave shapes, the DCW value adjusts the oscillator's harmonic content such that minimum setting produces a sine wave, while maximum setting produces the selected wave shape. For resonant-type wave shapes, the DCW value instead controls the perceived resonant frequency. The DCW can be modified using an 8-stage envelope, thus changing the timbre of the sound over time. In this capacity, it was described by Casio in the CZ-1's manual as being phase distortion synthesis's equivalent of the VCF (voltage-controlled filter) in analogue synthesisers.
Digital Controlled Amplifier (DCA) The DCA (which determined how loud a given oscillator was at a given moment) was also modulated by another dedicated 8-stage envelope generator. The DCW and DCA also had a "key follow" feature; which determined how much higher notes affected a sound, making the DCW have a more dull sound with less harmonics with higher notes, and making the DCA envelope faster for higher notes.
Modulations
8-step Envelope Generators (EG)
The envelope generators in the CZ synthesizers were far more flexible than a traditional four-stage ADSR envelope; they were eight stage envelope generators where each stage had a rate and level value. The rate value determined how fast the envelope would move; the level value would determine what pitch/filter cutoff/volume the envelope would have. Sustain and End point could be assigned to any stage of the envelope.