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Casio HZ600

Portable Keyboard

Article from Music Technology, November 1987

Budget polysynth or home organ accessory? Casio attempt to find another gap in the market with Spectrum Distortion synthesis. Nicholas Rowland finds it's not too far from old-fashioned analogue.

Falling somewhere between the old VL-Tones and their recent CZ range of synths comes Casio's latest, but will it have the same impact as either of its disparate relatives?

CASIO HAVE COME a long way since the days of singalonga watches and the classic VL-Tone. In a few short years they have entrenched themselves in the serious music market with equipment that has favourably combined desirable features, quality and low prices. In home keyboards too, they've managed to bring hi-tech notions like programmability, sampling and electronic percussion within the comprehension and budget of the (wo)man in the street.

Casio's latest keyboard product is intended to tempt the browsers in Woolies to move on from "synthwah" presets, auto-bass samba accompaniments and little yellow pads that set dogs a-barking every time you touch them. Enter the HZ600.

In spite of a healthy selection of factory sounds, the accent here is very much on user-programmability. The HZ600 is an eight-note polyphonic synthesiser featuring 61 full-size keys, a split keyboard facility, a basic MIDI spec and in-built chorus, plus pitch-bend and modulation. And with a reasonable price tag of £349, it continues very much in the "affordable" tradition of the CZ101 and CZ1000 synths which have found much favour in both amateur and pro circles.

Where the HZ600 differs from its illustrious predecessors is in its method of synthesis, a system which Casio have seen fit to call "Spectrum Distortion". Obviously this represents some offshoot of their well-established phase distortion system, but any more specific details are difficult to come by. (Even Casio's representatives here in England couldn't enlighten us further.)

Unless there's something hidden up someone's sleeve, spectrum distortion involves little more than is usually associated with subtractive synthesis, certainly if the list of programmable parameters on the front panel is anything to go by. From this you can make out that the HZ600 actually features two sets of sound generation circuitry, each completely independent of the other. Roughly speaking, each set follows the same principles, with one a mite more sophisticated than the other. This is used to create what, in Casiospeak, are referred to as the Upper Tones. These are the voices which apply to the upper part of the keyboard when the HZ600 is in split mode, but which in single mode will play across all the keys. The less comprehensive spec is reserved for the Lower Tones, which as the name implies can be played by the lower notes in split mode, but which in single mode cannot be accessed.

Incidentally, there are three pre-programmed split points to choose from (F2, C3 and F3) selected by repeated pressing of the Split function key. If these don't appeal, hard cheese, you can't redefine them. If you're then left trying to squeeze a bass line into the available number of notes you can always transpose the entire keyboard by +6 or -5 semitones to compensate.

Spectrum Distortion

TAKING THE UPPER Tones first, we discover a digitally-controlled oscillator which generates a total of 31 different waveforms: standard triangle, ramp and square shapes, plus some interesting variations which vaguely resemble camels negotiating mountain ranges. These can then be modulated using the LFO section (referred to as Vibrato) and further modified by a VCF and DCA. In fact, if you're familiar with basic analogue synth circuitry, you'll quickly realise that the parameters involved here are little different from the keyboards of yesteryear. The more observant will also notice the absence of any noise generating circuitry, though a couple of the waveforms do specifically produce this effect, so all is not lost when it comes to creating those snappy electro snares.

Where the lower tones are concerned, only 15 waveforms are available, though, judging from the illustrations in the manual, all fifteen represent further variations of the ones used for the upper voices (camels negotiating the pyramids). Here also, where the LFO is concerned you're limited to just one control: vibrato on, off and Delay. Otherwise, the various parameters and the extent to which you can alter them are just the same.


TO DEMONSTRATE WHAT can be done with all this, Casio have provided some 60 factory programmed Tones: 40 in the upper section, 20 in the lower. In each group, half these sounds are Preset which means they're in ROM and cannot be altered: the other half are Internal (stored in RAM), which means they can be used as the starting point for your own programming.

"If you're familiar with basic analogue synth circuitry, you'll realise that the parameters involved here are little different from the keyboards of yesteryear."

Three switches to the side of each bank of tone select buttons allow you to access voices from either Preset, Internal or Card tones. The latter refers to an optional RAM card (the RA100) which will allow you to load and save a further 180 voices, 120 of which are assigned to the Upper groups, 60 to the lower. Note that like the dual tonal structure, the memories of the HZ600 are mutually exclusive. In other words you can't save any upper tones to the lower tone memory locations and vice versa.

The 60 onboard voices nominally cover the usual range of sound groups: keyboard and mallet instruments, wind and brass, strings and special effects (sirens, explosions, typhoons and so on). One thing that immediately puzzled me about the arrangements of the presets was that there were virtually no bass sounds assigned to the lower tone banks apart from "Synth-clavi". When you consider that the advantage of splitting the keyboard is to combine a bass with a rhythm or lead sound, this seemed a strange oversight on Casio's part.

These preset titles proved extremely approximate as a quick tinkle on none-too-responsive plastics soon revealed. In other words if you're looking for the sort of synth presets which imitate rather than approximate to their acoustic counterparts, the HZ600 might prove something of a disappointment.

In general, to say that Casio's technicians haven't done the HZ600 any favours through their pre-programming is something of an understatement. Most of the sounds come across as rather thin: characteristics which I suppose might have been anticipated just by looking at the parameter structure of spectrum distortion. Admittedly you can beef up the voices with a touch of the internal chorus (of which there are three modes: Weak, Deep and Weak But Fast), but for the most part this simply isn't enough. What adds to the generally fizzy feel is the fact that, like the Korg Poly 800, there is only one filter per voice rather than for each note. Hence every time you play a new note, the filter retriggers. Sounds kinda cosmic, Man.

The best sounds are ones which the Casio engineers always seem to be good at programming - those ethereal, synth-flute voices with names like Fantasy and Magical Wind. Perhaps it goes to show that those VL-Tone days are not so far behind after all.


BUT YOU KNOW what they say: if you don't like the way a job's done, do it yourself. So let's have a look at the HZ600's programming system.

This involves two buttons, a dial and an LCD. The buttons are labelled Mode and Data. After selecting a voice, editing a parameter is a simple matter of pressing Mode, then dialling up the number of the parameter (the list on the front panel comes in useful here). Pressing Data then allows you to alter the value of that parameter, again using the dial. At any time you can compare the effect of your editing with the original voice just by pressing the voice select button. Press it again, and you return to the edit. On the whole, it's a system which is extremely easy to get to grips with. There are some disadvantages. For example, a set of plus/minus buttons would have helped, as it proves a tricky job using the dial to quickly alter a value by just a single step.

"One thing that immediately puzzled me about the arrangements of the presets was that there were virtually no bass sounds assigned to the lower tone banks."

Once you've grasped the basics, a little patience will yield some quite acceptable sounds of your own. Naturally the onboard presets are a good starting point, and, even if these don't inspire, Casio have included further patch data in the back of the manual. Providing you resign yourself to the fact that the HZ600 is never really going to give you rich synth textures, it's possible to come up with bright brass, string and lead synth sounds. It's a shame that upper and lower tones are available only in split mode, as the facility to layer sounds would have considerably expanded the scope of the instrument.

All editing has to be carried out from the front panel. Unlike the CZ101, there is no MIDI dump facility which would allow any bright computer spark to come up with an on-screen editing package.

While on the subject of MIDI, as I mentioned earlier, the MIDI spec is fairly basic. When set up in single mode, the HZ600 transmits and receives in MIDI Mode 3 (Omni off, poly). MIDI channel info is programmable, but for some reason, you're only given the choice of 15 channels (1-15). In split mode, both parts of the keyboard will send and receive independently (including Patch Change data) effectively giving you separate control of two other sound sources. In this mode, the MIDI channel for the lower section must be set to the number above that of the upper part. Also note that when in split mode, the lower part will not send or recognise pitch or mod wheel data.

MIDI In, Out and Thru sockets take care of all the to-ing and fro-ing. They share the back panel with sockets for Left and Right line out, foot volume and sustain pedals, a master tuning control, a port for the RAM card and the 9V DC power input (which with a special adapter will allow, of all things, the HZ600 to be connected to a car cigarette lighter - gives a whole new meaning to the phrase in-car entertainment).


THE HZ600 SEEMS intended to bring the home keyboard user into the unfamiliar territory of user programmability and interfacing with other MIDI instruments. The HZ600 represents a modest enough investment when compared with rival manufacturers' synths, but in the face of the current discounts on, say, the CZ101 and CZ1000 it's a different story. For a start, these models have greater editing flexibility with computer software, a more expansive method of synthesis (in my opinion) and better MIDI implementation. I know which I'd prefer to open my wallet for.

Then again, the HZ600 is ideal for someone who just wants to dip their toe in the water to test the temperature. The spectrum distortion synthesis structure is not the most sophisticated in the world, so, after the briefest glance at the manual it's easy enough to get the programming underway, even if at first you're not entirely sure what you're doing. In that respect it's an extremely user-friendly synth, which gives it the edge over the DX100s and DX27s of this world.

I suspect though, that it's destined to remain in the sitting room with perhaps just the occasional outing to the end-of-term battle of the bands. It lacks the facilities and the sound capabilities to follow the cheaper CZ's into professional and semi-pro situations. I don't know what plans Casio have for the future of spectrum distortion, but on the evidence of the HZ600, it doesn't necessarily result in a synth of many colours.

Price £349 including VAT

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Fostex X30

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Sonus MasterPiece

Publisher: Music Technology - Music Maker Publications (UK), Future Publishing.

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Music Technology - Nov 1987

Donated & scanned by: Mike Gorman

Gear in this article:

Synthesizer > Casio > HZ600

Gear Tags:

Digital Synth
Phase Distortion

Previous article in this issue:

> Fostex X30

Next article in this issue:

> Sonus MasterPiece

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