by Tomás Mulcahy
http://www.madtheory.com

This post is a work in progress since June 9th, 2002.
September 2006: First web version completed.
October 11th 2006: Some typos corrected.
December 31st 2006: New references added.
January 1st 2007: Corrected name of Casio’s first keyboard.
October 13th 2008: improved explanations of parameter values,
envelopes, LFO, and tape storage.
February 13th 2009: corrected name of Yukihiro Takahashi. Thanks to Michael Betancourt.
March 8th 2009: Sales figures and new references and links added.
June 23rd 2009: Added info on DAC frequency response.
August 30th 2009: Created historical timeline; added link to Wiki and US patent.
March 17th 2010: Added info about DAC offset calibration; revised pricing information.
May 22nd 2012: Fixed some typos.
April 16th 2015: Fixed some typos.
February 16th 2019: Added video and link to Toshio Kashio museum, review of Virtual CZ.
September 18th 2021: Added single cycle loops of CZ-101 waveforms.
March 25th 2023: Lost the single cycle loops 🙁
March 19th 2024: Edited info about UI, added info about sequencer bugs; added info about muzines Patchworks

History of development
1980 Casio introduced the Casiotone 201, their first home keyboard. A great product and favourable exchange rates allowed them to achieve great success in Europe and the US.

1982 Messrs. Ishibashi and Masanori of Casio patent PD synthesis.

1983 the Yamaha DX7 was introduced, and soon became the biggest selling synth ever.

1984 Casio wanted part of this market, and after a two-year development period, they came up with a £30,000 system called the COSMO SYNTHESIZER which was was debuted at the ARS Electronica. The system was based on Casio’s own office computer called the FP-6000, which itself was pretty advanced at the time, with features like a 29 bit co-processor. It was a general development system on which sequencing, phase distortion synthesis (PD) and rudimentary sampling were possible. One was built for IsaoTomita but it never went into mass production.

Here is a video of Tomita’s system exhibited in 2015 at the Toshio Kashio museum.

The only other PD synth in the world was the similarly computer based Con Brio ADS, on which it was termed “phase modulation”. It seems that it was fashionable at the time for companies to develop incredibly expensive computer based synthesisers, but only Fairlight and the Synclavier would have any measure of success in this rarified market. Casio was a calculator manufacturer whose expertise lay in mass producing LSI chips. They had already produced the VL- Tone, a bizarre calculator/ synth combo.

1985 In February Casio brought their expertise to the pro synth market with the CZ-101. With its 4 octave mini keys it fitted in with Casio’s pocket calculator image. Its diminutive size contrasted with its big sound, and soon CZ sales were in DX7 territory.

1989 Ed Alstrom, Casio’s marketing manager, estimated 80,000 CZs sold worldwide, making the CZ-101 one of the most popular synthesizers ever.

FM vs PD
Apart from the US patent here is very little information available on how Casio developed phase distortion, but it’s very likely that it was inspired by John Chowning’s FM. In Casio’s version, an envelope directly modulates the phase of a waveform, of which there are eight to choose from. In Yamaha’s original implementation of FM, waveforms are grouped together in eight algorithms, and the envelope controls the frequency of one waveform, which then modulates another waveform or waveforms depending on the algorithm. Technically, they’re different systems because the Casio operates in the time domain (i.e. phase) and the Yamaha works in the frequency domain, but the similarities are clear enough. Instead of introducing a completely new method of synthesis á la FM, Casio came up with a cost effective way to digitally implement the sound and feel of a proven technology- analogue subtractive synthesis. Furthermore, the design also has some features that give it a unique character.

User Interface
The user interface is the usual “parameter access” which was in vogue at the time. There’s a pair of data increment/ decrement buttons, and a dedicated button for each parameter- just like the DX7 except there is no data slider. So you have to wait for the values to scroll by instead of dialling them in directly. Compared to other similarly priced synths of the day such as Korg’s Poly 800 and the Crumar Bit One, the Casio is a breeze to use.

The parameters have an arbitrary value range of 0 to 99. The exception is the detune which is in cents, semitones and octaves. If you’re using a graphical computer based editor most of the time, this is not really a problem, but when you want to make a quick tweak on the synth itself, it can be a little frustrating. Ideally the scales would be in deciBels and milliseconds, but no editor I know of has worked these out for the CZ series.

Synthesis on the CZ

1. Architecture
There are two discreet synths in a CZ, called “Lines” 1 and 2. Each line has an oscillator, the equivalent of a filter section called the DCW, and an amplifier section called the DCA. Detune only works when you mix or “add” two lines together. Line 1 can be added to itself, allowing one line to be detuned, and similarly Line 1 and 2 can be added, and only Line 2 can be detuned. So you cannot easily combine positive and negative detunings. In practice, this is a minor limitation.

2. The envelopes
Each of these sections has its own eight-segment envelope generator. Each segment of each envelope can be as short as one millisecond or as long as a minute, and the level in any segment can be either rising or falling within a given range. A value of 99 is the fastest rate or highest level, a value of 0 is the slowest rate or lowest level. Using the first two segments gives you the classic ADSR type envelope, and after that it can be as complex as you like. The envelopes are probably the most unique and powerful feature of the CZ. Unlike most synths up to 1984 there is a dedicated envelope generator for pitch, as well as the usual timbre and volume, so with the two lines there are six in total. That’s a lot of control, and some very complex effects can be created quite easily. It is possible to use the pitch envelope to combine positive and negative de-tunings for example, or to add subtle analogue style drift to the oscillators.

3. LFO?
There is one LFO, and this is for vibrato only. It would be nice to have one for each section, but the envelopes make up for this shortcoming in most situations. The ultimate no compromise solution would be envelopes that looped, allowing extremely complex waveforms. Intriguingly, this facility is available on Casio’s FZ-1 sampler. There are four wave-shapes and the onset can be delayed. The depth setting can be over ridden on those CZs that have a modulation wheel. On the CZ-1000 and 101, there is a switch instead of a wheel, so depth is fixed.

4. Oscillators
At the heart of the CZ are eight distinctly different, harmonically rich waveforms: sawtooth, square, narrow pulse, a broader rectangular wave, a “split” saw/ square, and three “ringing” waves of the type that resonant filters produce in self oscillation. These waveforms were clearly designed to sound “analogue”. I’ve recorded the raw oscillator output of two different CZ-101s and come up with the same interesting results:

Waveform name	Theoretical wave shape	Actual Shape generated by CZ	Comment
Sawtooth			Positive going instead of negative going.
Square			Nothing like a square, but it is positive going at least.
Pulse			Inverted.
Double-Sine			Inverted.
Saw-Pulse			Negative going, with a twist!
Resonance 1 (sawtooth)			Inverted.
Resonance II (Triangle)			Inverted.
Resonance III (Trapezoid)			Inverted.

According to Richard Young, UK product manager at Casio in the early eighties, Casio’s R&D “were very aware that digital sounds weren’t the be all and end all of sound creation and that it was important to make certain sounds warmer…” Clearly Casio were well aware of the advantages of the imperfections of analogue synthesizers, so they developed the CZ series with the co-operation of Yukihiro Takahashi of the Yellow Magic Orchestra, and Isao Tomita. I think it’s safe to assume that the resonant waveforms are modelled on the modular Moog- they certainly sound like they are. The rest of the waveforms share traits with those produced by analogue synthesisers such as the Yamaha CS series and Sequential’s Prophet 5. So much for what it sounds like- in actual fact, the resonant waves are generated by adjusting the tuning of two synchronised sine waves, with some additional processing to remove the noise that this generates. Sounds like Chowning’s FM again, doesn’t it? Clearly Casio’s engineers knew what they were doing- the waveforms they produced are the same musically useful ones used by the likes of Tomita and other talented synthesists.

You can select any wave on its own, or combine any two. The combination works by making a single cycle into two cycles, with waveform one making the first cycle and waveform two making the second. Discounting duplicate combinations, there are 33 possible waveforms- again, a lot of flexibility.

5. Filter (kind of!)
The next step is the Digitally Controlled Wave-shaper (DCW). This works effectively like a filter, except that the only way to control it is via the envelope generator. There is no global cutoff setting, apart from whatever levels you choose in the envelope. At level of 0 it is “closed”, and a sine wave is produced. It’s easy to set the envelope to sweep smoothly from 0 to the maximum value of 99, and get the standard analogue filter sweep sound that was very difficult to achieve on the DX7.

For the waveforms with broad spectra, such as the sawtooth or square, the sound of the wave-shaper is very close to that of an analogue lowpass filter. For the waveforms with narrow spectra, like the so-called ringing (resonant) waveforms, the frequency of the ring increases as the wave-shaper opens, just like a resonant or bandpass filter. The CZ is actually carrying out time-domain processing, but as far as our ears are concerned it’s all in the frequency domain. The waveforms Casio chose are a very clever way of using minuscule DSP power to simulate different types of analogue filter. The distinct advantage over Yamaha’s FM that you can readily hear the effects of changing the waveform or the envelopes. Moreover, none of the parameters interact, e.g. if you change the pitch envelope, the waveform and amplitude envelopes remain the same. This makes it a much more manageable system than FM- you can mess around and get good results in time, or you can apply some theory and get excellent results very quickly- very much like a good analogue synth. Casio’s approach doesn’t give the perfect model of a typical analogue synth, but it has enough quirks to make it worthwhile in its own right, and retains the overall feel that makes subtractive synthesis so popular.

Additional features
Talking of quirks, the ring modulator is quite interesting. In the same way that the DCW doesn’t quite sound like a filter, the ring mod sounds rather odd too if you’re used to analogue ones. And it’s not simply a logic NAND gate- there’s more complex mathematics involved. In fact, there are 3 different types of ring mod available if you use the Inside CZ SoundDiver profile from the Sealed website. Nonetheless, the CZ is strong on all types of clangorous bell sounds. Another useful quirk is that the two lines sometimes do not trigger perfectly simultaneously, so just layering Line one against itself (setting line select to Line 1+1′) can occasionally cause pleasant random phasing. All these little design flaws add up to make a synth in which the whole is greater than the sum of its parts, just like any other classic instrument.

Portamento and chorus
All the CZs feature polyphonic and monophonic portamento. It’s the constant rate type which some players love and some hate (the VZ series improved this by allowing you to choose between constant rate or constant time) and all the CZs store this as a global setting, except the CZ-1, which can store it in for each of the 64 “combinations” (i.e. performances). This is an extra layer in the patch hierarchy, allowing storage of layers, splits and multitimbral performances. In solo mode the CZ is last note priority- again, some players favour this. The CZ-3000, 5000 and CZ-1 featured a noisy built in chorus effect which only had a depth control. It sounds pleasant enough and softens the sound nicely, but it’s easily beaten by any of the Roland units. The CZ-1 also stored chorus on/ off (but not depth amount) as part of a combination.

MIDI functionality
Back in 1984 the CZ’s ability to play four different sounds simultaneously was a big deal. The CZ-101 and its sister CZ-1000 were the second ever multitimbral synthesisers- the first being the Sequential Circuits Six Trak (from the same year). Even though they are up to 8 note polyphonic, the 101 and 1000 are restricted to 4 notes in multimode, each part is monophonic, and chosen channels must be sequential. A further limitation was the lack of separate outputs. The CZ-1 was a step up with two separate outputs, but retained the restriction of manual note assignment found on the CZ-5000 internal sequencer. The notes were not dynamically shared across the parts- you had to decide how many notes each part needed from a maximum of eight. But at least the CZ-1 is polyphonic in multimode, unlike the CZ-5000 and 3000 which are limited to 8 monophonic parts via MIDI.

Casio sequencer
The CZ-5000 is the only instrument in the range featuring a sequencer. It is the equivalent of two Casio SZ-1 sequencers. By today’s standards it’s basic, but very easy to use. The step programming is certainly worthy of note. There are dedicated buttons for note durations and rests. Phrases of different lengths can be programmed on each track, then looped. With a mute button for each track, it’s very easy to create interesting polyrhythmic music on the fly. It can also record velocity from an external keyboard. The memory capacity can be up to 7200 notes assuming you don’t use any controller data. Only one “song” at a time can be held in memory. Storage is to data cassette, which was slow but reliable. Sys-Ex can be used if you have a computer based librarian capable of making the necessary dump request. Used in combination with a more modern sequencer it can be quite a creative tool. The sequencer-less CZ-3000 goes for about the same money today as the CZ-5000. There appear to be some bugs in the sequencer- certain sounds trigger an ascending spiral of pitch when their track is muted. The SZ-1 sequencer bug is fortunately not replciated- where programmmed repeats always have a small pause before the repeat.

Other useful things
The RA-3 RAM cartridge can be used to expand the 101 and 1000’s total memory to 32 user locations. The same cartridge will hold 32 sounds on the 5000 and 3000, but unfortunately these cannot be accessed directly. Instead, the cartridge sounds have to be loaded into internal RAM, so you’re still limited to 32 locations. The CZ-1 has 64 locations internally and in addition can access the 32 locations on the RA-3, but without the patch names, velocity or aftertouch data. The rare RA-5 cartridge had 64 locations and is fully compatible with the CZ-1.

The CZs have a pretty good MIDI implementation for the time, and consequently are well supported by modern editor librarians. I used to store my CZ-5000 patches on a freeware Mac program called CZ librarian 3.0. Later I upgraded to Opcode’s Galaxy. Thankfully, CZ Librarian used the same file format, so even today I still have all my old sounds easily accessible. I made one large sysex file of all the sounds for Emagic SoundDiver. They now reside in both Arturia CZV and PluginBoutique VCZ.

The factory presets are typical of those found on other Japanese poly-synths of the time- bright, bland but with one or two gems. They are good basic starting points for most types of sound though. There’s a wealth of patches available on the net. Muzines is a very useful resource- all of the CZ patches from the Patchworks series are downloadable, Ben@muzines converted most of them and I converted a few myself for Arturia CZV. he CZs are so easy to use that there’s really no excuse for not getting your hands dirty with a bit of programming.

Which CZ is the best?
The CZ-101 and CZ-1 are probably the most desirable of the series; the 101 simply because it’s so small and cute! The CZ series excels at bass sounds, so the four note polyphony is ample. The CZs are also very good at organ and electric piano sounds. Particularly with the latter, the velocity sensitivity of the CZ-1 is a must. The keyboard action is not great- the velocity and aftertouch are far more musical when you have a decent keyboard controlling it via MIDI. Casio’s own VZ-1 keyboard, for example, is excellent. It’s a pity that Casio never made a rack-mounting CZ.

Sampling
CZ sounds tend to sample very well, so a 101 would be a useful investment for someone who likes to make their own samples. Sounds with complex envelopes can occasionally be awkward, requiring more multi-samples. Most of the time though, disabling the vibrato is all that’s required to avoid a lot of multi-sampling. Similarly, many patches use the second line for nothing more than a detuning to fatten the sound. Sampling just the one line and detuning on the sampler is much better. Even sampling the basic single cycle oscillator waveforms provides some very useful raw timbres that provide plenty of scope for a sampler with a good synthesis engine. These waveforms are harmonically rich, and the superior transposing on a modern sampler really lets this shine through.

Speculation- the synth that could have been
Casio decided to replace the hugely successful CZ series with the VZ series. These featured a completely new synthesis engine called interactive phase distortion (iPD). This method had the potential for more complex sounds, but combined with a very poor user interface were very frustrating synths to use. Programming is very difficult even if you use a computer editor. Some interesting sounds are possible but programming is not a rewarding experience. It’s impossible to predict what will happen when using complex modulations, and parameters are very interactive. I suppose that’s why they called it iPD. Unfortunately, it was not the selling point Casio hoped it would be.

If Casio had just made the VZ the equivalent of two CZ-1s, and maybe included the waveform drawing from the FZ samplers, an expanded version of the sequencer from the CZ-5000, a floppy disk drive and patch compatibility with the older CZs, they might have had another hit. Roland and Yamaha have been around for so long because they have always carefully built on past successes. Unfortunately, Casio were just too radical with the VZ and as a result of its failure they left the pro synth arena.

Casio synthesiser range (with honourable omissions)

Model	Polyphony	Multitimbral parts	Onboard patch memories	Other notable features
CZ-101/ 1000	4/ 8	4 (monophonic)	16	4 octave keyboard, 101 has mini keys and push buttons on the panel, 1000 has fullsize keys and membrane switches on the panel.
CZ- 3000	8/16	8 (monophonic)	32	Like a 5000 without the sequencer. Tape data storage of patches.
CZ- 5000	8/16	8 (monophonic)	32	8 track polyphonic sequencer. Tape data storage of patches and sequences.
CZ-1	8/16	8 (polyphonic)	64	Velocity, aftertouch, 2 semi-assignable outputs, 64 layer/ split memories.
VZ-1/ 10M	8/16	8 (polyphonic)	64	Velocity, aftertouch, 2 assignable outputs, 64 layer/ split memories. Two assignable mod wheels.

Technical- the DAC
Internally the CZ digitally generates a compressed waveform that is expanded in the analogue domain, a process known as compansion, which allows the 12 bit DAC to produce the theoretical equivalent of 14 bits. It is based on the same principle as dbx noise reduction, where the signal is recorded with compression and sympathetically expanded on playback. As anyone fortunate/ unfortunate enough to have used this system will know, it tends to add a certain colour to the sound, caused by the expander mis-tracking. Punchy lows, breathy highs, distorted dynamics and honkiness are among its traits. To give you an idea of the sound, the same method was used most notably in the Roland Dimension D and (as a very unpopular option) in the ADC of the Fairlight CMI II. It’s no coincidence that these devices are valued for the colouration of the sound.

The CZ-1 DAC runs at a sampling rate of 40kHz, and the filter rolls off at 20kHz. It could be interesting to completely bypass this filter circuit and possibly realise an improved frequency response/ lower noise floor. This seems to be common with Casio keyboards, where a heavy-handed LPF is used to lower noise at the expense of a duller sound.

Improving the sound
The service manual is very good. These are relatively easy synths to work on. Most issues are very easy to fix, if you are confident about opening up the instrument and reading a schematic. One very common problem is best described as a kind of gritty “low bit depth” grunge which gets worse the more notes you play in a chord. This is not the natural state of the instrument. It’s actually the compander mis-tracking (see DAC description above). The procedure to fix this is detailed on page 59 of the CZ-1 service manual: DAC offset voltage adjustment. Note that it’s the same for all of the CZs. A voltmeter is suggested, but actually it can be done by ear. On the CZ-1 (and I guess the 3000 and 5000 also) the trimmer VR3 is located under the keyboard so it is necessary to completely dismantle the whole instrument. As with any electronics repair job, it is sensible to ensure that you have a large and tidy work area, otherwise you will loose screws! It is also a good idea to photograph each stage so that you can put everything back where it belongs.

A virtual CZ
1. ReFX PlastiCZ (discontinued)
This plugin is the closest I’ve found on the Mac to a Casio CZ. It is a phase distortion synthesiser, but it lacks many of the Casio’s features. The basic waveforms are certainly bright, but they are not as harmonically rich as the Casio. The “resonant” waveforms in particular are a disappointment- they have a harsh metallic sound with limited timbral variation via the DCW. The envelopes are simple ADSR types, and there are only two of them, whereas a CZ has six. There is no LFO, a pretty serious omission. The ring modulator is pretty good, possibly better than that of the CZ because it sounds like a real one, or at least a model of a real one… One useful feature which the Casio’s don’t have is that you can mix the output of the ring modulator with the untreated outputs of the two lines.

The interface is excellent, among the best I’ve seen in any soft-synth, and the built in effects are a worthwhile bonus. Unfortunately the range of sounds is severely limited compared to a Casio, and the plugin has none of the character of the original synth. But I think, with a few little tweaks- better waveforms, 8 stage envelopes (six of them!), an LFO and CZ patch compatibility- this synth could easily replace a CZ. I suggested all of this to reFX but they decided that the market wasn’t big enough to justify the work. A pity!

2. Oli Larkin’s Virtual CZ (2014)
This has two fantastic features that I think should be standard in any synth emulation:
1. It works as an editor for any CZ, and can read CZ SysEx files (but does not support CZ-1 Operation Memories)
2. The preset browser works across all plugin formats (VST, AU, AAX etc.)

In addition to emulating the CZ, it features superbly accurate emulations of both Casio and Roland chorus units. Another great feature is a Unison mode which sounds fabulous with most sounds, but is unfortunately monophonic (polyphonic is being considered in the next update).

Oli had difficulty reverse-engineering the Casio envelopes precisely. In my limited understanding of it, the real machine works using look up tables, and has some sort of variable scaling he could never quite work out. In practice, this means that some sounds will not be the same as the hardware. I found this particularly the case with some percussive sounds, or sounds with a fast attack. But not all of them!

In my experience this is the best editor available for the CZ. It’s much easier to do common tasks such as adjusting brightness with the DCW dial. You have the option of using simpler ADSR envelopes instead of the Casio multi-stage envelopes. Plus of course you can audition your sound immediately on the plugin, or even without a real CZ attached. Great for working on the move!

In general this plugin sounds smoother and bigger than the real thing because it does not closely emulate the companding DAC. This is a good thing! However because it is not a 100% perfect emulation, I often use my deep-sampled CZ patches in Kontakt instead of the plugin.

Pricing
As of 2006, each of the CZ instruments seem to sell for around 100 to 160, in UK pounds, Euro or US dollars. The CZ-101 tends to be more highly priced, presumably because of its small footprint. The CZ-1 can be had for around 200, but it’s quite a rare instrument. The CZ-1000 is the most widely available, because it was the best value in 1984 with its full size keys.

There are a lot of CZs around, and they are very reliable machines even today. Common problems are failed displays and minor power supply issues- 101s often cannot be powered from batteries. This also means that memory is lost on power down. A computer based editor librarian solves both of these issues, apart from the inconvenience of having to reset the instrument and reload your patches. All good service centres can repair a CZ without any major difficulty. Given the low second hand prices and the number of CZs around, spare parts should not be an issue either!

References

*Alstrom, Edward in
Powerplay VZ!
De Furia, Steve ; Scaccaferro, Joe.
New York: Hal Leonard Publishing Corp. 1989
Crombie, David and Wiffen, Paul

The Casio CZ book
London: Amsco/ Wise Publications, 1986
(thanks to A. Miles for the book)

Cosmo
The history of the cosmosynth and patches to download.

Moog, Bob
Unexplored resources of the Casio CZ-101
Los Angeles: Keyboard Magazine, April 1986

Schlesinger, Andrew
An Insider’s Guide to Casio CZ Synthesizers
ISBN: 0882843672
NY: Alfred Publishing Company, 1988

Sealed
Technical details on the hidden extra parameters in the CZ-1, and a Sound Diver profile to access them.

Tom Wiltshire’s Electric Druid site, with an excellent explanation of PD synthesis.

The Wikipedia article on PD synthesis.

Casio’s patent of PD synthesis.

CZ Waveforms click to download

Toshio Kashio (founder and designer of Casio) museum website.