The Casio CZ101 was a curious product when it was released in the mid-80s.

Casio, of course, were better known for making calculators and they had dabbled in 'toy' musical instruments such as the VL-TONE but then, out of nowhere, they released the CZ101.

It was small with a 4-octave mini-keyboard and it looked like Casio were up to their old tricks and had released yet another toy keyboard! In fact, nothing could be further from the truth!

Behind this unassuming little panel was an 8-voice polyphonic digital synthesiser offering yet another new form of synthesis known as Phase Distortion.

Not unlike FM synthesis in some ways, by changing the phase angle of a any of the supplied waveforms, you could alter the harmonic content of the selected waveform. With no phase distortion, you hear a sine wave but as the phase distortion is increased and the waveform's phase angle is altered, so the waveform becomes closer to the selected waveform. The resulting effect is pretty much the same as sweeping a lowpass filter. The waveforms supplied included Sawtooth, Square, Pulse, DoubleSine, Saw-Pulse, Resonance I (Sawtooth), Resonance II (Triangle) and Resonance III (Trapezoid).

So, using Square as an example, with no phase distortion, you get a sine wave and as the phase distortion amount is increased, odd-numbered harmonics are added and the sound gets brighter and brighter until at maximum, you have a square wave - the audible result was not unlike passing a square wave through a lowpass filter and opening the cutoff frequency.

The other waveforms gave access to other sounds and the various 'Resonance' waveforms allowed something resembling a resonant filter sweep to be created.

You could control the amount of phase distortion using LFOs and envelope generators that allowed you to go some way to mimicking many typical analogue sounds. However....

The CZ101 was an all-digital synth and sounded like one! it could create some interesting 'digital' synth sounds but as an analogue synth emulator, it sounded rather thin and weedy! However, it was possible to split the eight voices to set layers which could be detuned for a fatter sound and so, used as a 4-voice synth, it was possible to create some decent sounds.

It had an impressive spec too - three 8-stage envelopes per voice (one for pitch, one for PD waveshaping and one for amplitude) and several LFOs, it also had a ring modulator and noise generator and, amazingly for the time, it was also four-part multi-timbral with a respectable MIDI spec. In all, despite its toy-like appearance, it was quite a good little synth. It was probably not suitable as your only synth but as a cheap expander, it was (and still is) a useful musical tool.

Casio followed the CZ101 with larger models with full size keyboards and more sound shaping facilities culminating in the VZ series of keyboards and modules. However, whilst there was a large user-base out there, the product line wasn't a huge success (it was, after all, yet another product battling it out with the DX7!) and the CZ/VZ-series were eventually disbanded.

The Nostalgia Casio CZ101 sounds come from Simon Metson who has given us a selection of brass and percussion sounds and also from Gareth Lucking who has given us a multi-sampled CZ cheezy organ sound. I'm extremely grateful to both donors.