Casio CZ-101 Review

A review of the Casio CZ-101 synthesizer, from the charitable perspective of someone with experience in ugly, digital noise: An industrial musician.
TL;DR: A novel digital synthesiser capable of creating the beautiful bells and squeaky basses you'd expect from an 80s digital synth, but not much else. The CZ-101 is a nice, fun unit if you can pick it up for the right price. Overall though it doesn't really stack up against Yamaha's contemporary FM offerings.


The year is 1985. The music world is still in the grips of DX7 mania, and FM synthesis is completely reshaping the landscape of popular music. Yamaha's DX7 is quickly becoming the best-selling synthesiser of all time, and the world's biggest synth manufacturers are scrambling to catch up. Roland's technical R&D director Tadao Kikumoto —The man behind Roland's iconic TB-303— even spent a year searching in vain for a way to beat Yamaha's FM patent (Reiffenstein, 2004, pp. 275-276). While synth heavyweights Roland and Korg were stuck at the drawing board, calculator and watch manufacturing heavyweight Casio had their own homegrown answer to Yamaha's FM: Phase Distortion synthesis.

Casio filed their first patent for phase distortion synthesis in 1980, listing Masanori Ishibashi as the inventor. Until now they'd only implemented it in their Cosmo Synthesizer system —an ill-fated competitor to the Fairlight CMI— but in February of 1985 Casio would release the CZ-101, to much acclaim. Finally, there was a worthy challenger to the DX7. But how well did Casio's phase distortion synthesis stack up against Yamaha's FM offerings?

Initial Impressions

I knew what I was in for as I unboxed my new CZ-101. Warm basses? Lush strings? Screaming leads…? No. Casio's CZ-101 is something different entirely. Like Yamaha's FM synthesisers —whose shadows it lives in— the CZ-101 really shines at producing percussive, metallic timbres. I was in the market for a quirky, noisy synth that was capable of the unexpected, and I got just what I was after. Your mileage may vary, caveat emptor.

For an 80s digital synth, patch editing is surprisingly intuitive. Despite heavy reliance on paging and scrolling, the editing interface is clean and straightforward. Patch editing is facilitated by several rows of buttons, which make for a much nicer tactile experience than the nightmarish membrane buttons of Yamaha's DX series. The CZ-101 manages to sidestep the steep learning curve of Yamaha's FM synths through great interface design, and a clever, simplified implementation of phase distortion synthesis1. It didn't take long for me to create dark and brooding metallic pads that really pulled me in with their striking, harsh tones. Overall, the process of creating a usable patch from whole cloth is much easier than on an FM synthesiser. One minor annoyance I encountered with patch editing is that the CZ-101 does not ship with a usable initialised patch in the empty internal storage slots.

The presets are exactly what you'd expect. Ghastly strings, bright brassy saws… And the particularly evocative 'Fairy Tale' patch, famously used by Burzum.

Unfortunately, the device requires 5 D-size batteries to retain patch memory, and it has only a single monophonic line-out socket. The keys are not velocity sensitive2, and have a particularly flimsy quality to them. The device has a fairly wide non-backlit LCD screen, which is great by 80s standards. The DAC quality is on-par with what you'd expect: flat and muted. However with a bit of post-processing you can make it sound fantastic.


Diving into the synth engine itself, I was pleasantly surprised by its capabilities. For all it lacks in flair, the synth includes some surprisingly sophisticated features. The ability to control not just the level, but the slope of each segment in the 8-stage oscillator, waveshaper and amplitude envelopes for each timbre was a pleasant surprise. Yes, you heard me right. Not only did I say 8-stage envelopes for each feature (eight!), but I also said slope. Unlike your standard ADSR envelopes, you're not actually controlling the speed of each envelope segment but its slope. This subtle feature had me wondering why a value of 48 in the 'rate' field provided a steady, linear increase in volume, while a value of 36 was grindingly slow. I initially suspected there was some kind of configurable exponential slope to the envelope until consulting the manual. Another unexpectedly nice feature is the ability to control which of the 8 segments functions as the sustain and release segments, allowing you to use only the number of segments you need in a sound. Very cool.

The CZ-101's phase distortion synthesis works by modulating the rate at which a digital sine wave in memory is played back, while still preserving the oscillator's frequency. This speeding up and slowing down segments of the wave's playback distorts the sine wave into new shapes, introducing interesting harmonic changes into the sound. A great, simple explanation of the process can be found here. One illustrative example of this process is increasing the phase angle of the rising edge of the sine wave, while decreasing the phase angle of the falling edge. This distorts a sinusoidal wave into a sawtooth like form.

The CZ-101 doesn't have filters. Instead it features 'waveshapers' for each of the synth's two timbres. These waveshapers, and their accompanying envelopes, adjust the intensity of the phase distortion. The effect —while entirely different in theory— is not unlike that of a VCF, and can be used to create analog-sounding timbres with little effort.

Among its other features are a ring modulator capable of creating very interesting tones, and a very flexible key tracking facility for the oscillator, waveshaper, and amp sections. The second timbre can be used to ring modulate the first, and the first timbre can even modulate itself. According to this very interesting website there are some hidden features on the synth accessible only by SysEx. If you have a CZ-series synth definitely check it out!


This synth certainly features an engine designed by intelligent, forward-thinking engineers who had a genuine, inspired idea to explore. It was seemingly then belted and bashed into a budget unit fit for the hobbyist market. It's not a great quality instrument by any means, but it's a definitely fun synth to use. It's capable of some fantastic, beautiful bells, squeaky basses, and harsh digital noise. However it doesn't excel at much else. They've achieved a well-deserved cult status for reasons that this blog post will attest to, but for what it's worth the CZ-101 is certainly no 'desert island synth'.

The CZ-series synths don't appear to be particularly common, nor entirely rare. The Australian synth market suffers from highly inflated prices, so I totally overpaid for mine. From what I can see online, they're much less rare in the United States, and can be easily found for great prices. The CZ-101 is a nice, fun unit that can be picked up in good condition for a bargain price. However it compares unfavourably with Yamaha's FM offerings, which are not only more capable, but are of a higher quality overall. For not much more of an investment, one could pick up an actual DX7 or TX81Z.

If you're a fan of 80s digital synths like I am, jump on in. This is a fun device capable of some uniquely alien sounds. If you're a beginner to the synth world looking for a good place to start, my advice is to pick something else. A more well-rounded synth can be found more cheaply and easily elsewhere.


  1. The CZ-101 provides an array of preset harmonic waveforms created via phase distortion synthesis. This is in sharp contrast to Yamaha's DX series which required a much more nuanced understanding of FM synthesis to create useful waveforms.
  2. This might seem an absolutely unforgivable sin by today's standards. However the synth world was a totally different place in 1985. Before you judge too harshly, consider that Korg's Volca FM —a similarly priced synth made over 20 years later— doesn't even receive velocity over MIDI.