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Casio SK-1


Article from International Musician & Recording World, November 1986

A Fairlight small enough to slip into your 501's? Well, nearly. Jim Betteridge warms to Casio's supercheap sampler

Taking sampling in hand — the SK-1

We all know that sampling synths are getting cheaper, but this is ridiculous — 89 notes? And in addition to being a sampler the SK-1 is an auto-play keyboard and a synthesizer capable of additive synthesis. It's also dead tiny (18" x 6" x 1¾"), 2.65lbs (including batteries), and with the relevant power adaptors it can not only take its juice from a standard 13A socket but also from the cigarette lighter socket in your motor, if you have one. It has a 2½-octave mini keyboard starting at the F below middle C and finishing on a C, with four-note polyphony.

A Little Limited

Before I rave on further, a little stark reality must be injected; there are some very definite limitations here. Digital memory is still far from inexpensive and thus sample length is inevitably linked to price. Thus you will not be too surprised to hear that the SK-1 allows a maximum sample time of only 1.4 seconds. The sonic quality of the sample is also directly linked with the amount of memory available. This is an eight-bit system, as was the original Fairlight, and as such could be capable of very good quality samples. However, a stated sampling rate of 9.35kHz would suggest an approximate audio bandwidth of around 4.5kHz (half the sampling rate), which is less than a cheap cassette player. With this in mind it probably has to be admitted that you are not likely to yield any great rich musical harvest from the SK-1. It won't go any way towards replacing a Prophet 2000 or a Mirage, and probably must be considered as more of a sound effects capturer with occasional musical instrument imitation applications, and also possible as an inexpensive introduction to the art of sampling.

The four-note polyphony extends to the sampling facility. You record a single note or sound and then play back a chord of up to four notes. This is achieved by the digital equivalent of speeding the tape up: the original signal is read into memory at one speed and then read out at a faster rate for a higher pitch and a slower rate for a lower pitch. There are various problems with this process, one being that any substantial upward pitch change results in a 'Mickey Mousing' of the sound and a downward change makes a human voice sound like the bass voice in the Four Tops and affects other instruments similarly. The way round this is to 'multi-sample' a sound, where the instrument being sampled is recorded several times at different pitches so that when you play different notes on the keyboard you access different samples nearer to their pitch.

You may think it unnecessary to tell you that there is no 'multisampling' ability here, and certainly it would seem unfair to expect it at this price. There again the Yamaha VSS-100 at £179 does allow up to four samples to be taken across the keyboard, and it also provides a total of eight seconds sample time to play with.

Back on the positive side, the SK-1 does offer the possible advantage of 'looping'. This means that when the contents of the memory has been read once the 'read pointer' (like the playback head on a tape recorder) instantly loops back to a point nearer the beginning of the sample and starts reading again, and so the loop keeps on repeating itself until the key is released. In this way a 1.4 second sample of a continuous sound such as strings can go on indefinitely when played back. This is the same principle by which a harmoniser works and anyone who has used one of those will know that pitch changing a sustained note results in cyclic hiccupping — more or less noticeable depending on the nature of the sound and the quality of the harmoniser. The greater the upward pitch change, the faster the glitching, the lower the change the slower the glitching. Thus, a sustained chord using four notes, all hiccupping at different rates, does tend to sound a bit rough.

No Bruce Hornsbys

But what of the occasional musical instrument imitations? Even if great lush string sections are out (and they definitely are) the ability to take real sounds and inject them into your music is still valuable. I sampled a middle C from my Rogers upright piano and within about an octave or so range it produced an acoustic piano sound far superior to the standard low cost synthesized effort. Again, you aren't going to be able to do a Bruce Hornsby but within that octave register you could hammer out four note chords for basic rhythm that would sound fairly acceptable when set back a little in the mix.

I also sampled the sound of a screaming lead guitar going through a Mesa Boogie (so much going into so little) which turned out to sound quite powerful when used for chord work. I even exhumed my old clarinet and tried sampling a note or two from that. The result was absolutely dreadful, but I suspect that that was an all too faithful replication of the original.

Replicating sustained sounds that are intended to be forward in the mix is a little doubtful due to the 4.5kHz bandwidth, the noise and the glitching, but staccato sounds that don't have to sound exactly like anything and which are to be laid back a little in the final mix are actually quite possible. Looking again at the Yamaha competition (the VSS-100) one of the great features of the package is the inclusion of a cassette containing a large number of relatively hard to come by and extremely useful samples from the obligatory breaking glass and large orchestral stabs to more obscure instruments and noises. With the SK-1 there is no such tape and so it's down to you to steal things from records (and try and live with your conscience) afterwards or take a tape recorder with you to the next LSO concert you attend.

The sampling facility is just one part of the SK-1 repertoire. As mentioned it is also an autoplay keyboard and a (very basic) additive synth. On the electronic keyboard front there are eight basic sounds to choose from each with four-note polyphony: piano, trumpet, human voice, pipe organ, brass ensemble, flute, synth drums and jazz organ, all of which are quite impressive, although I could have done without the compulsory repeat echo effect on the human voice sound, making it impossible to have a sustained note with what was otherwise a very impressive sound. Probably the voicing is less impressive without the initial impact of the consonant. The sampled sound can be used as a ninth source for manual playing or auto-play. To smooth things out a little there is portamento and vibrato that can be switched in or out for any voice.

In Addition

Additive synthesis is based on the fact that any sound can be seen to be composed of a large number of pure sine waves at different frequencies and volume levels. On the SK-1 the synthesized sound is created from combining any or all of eight harmonics with their fundamental note. It is possible to determine the strength of each harmonic in the sound and you are given a number of examples as to how you can create the sound of real instruments. None of these was particularly realistic, probably because eight harmonics isn't enough to create very complex sounds and also because accurate replication depends on being able to move each sine wave up and down in time, which is understandably not possible with an instrument of this price. The whole process could be seen as an introduction to additive synthesis, but in practice it's musically rather weak.

A nice touch is that having chosen your basic voice, if you aren't happy with how it sounds you can then choose any one of 13 different 'dynamic envelope' shapes to give it a softer or harder beginning, or a longer or shorter tail, etc. Thus, if you've had absolutely no experience of synthesis before, this is an introduction to dynamic envelopes and their effect on sounds.

The rhythm section is a lot simpler with 11 preset rhythms to choose from, though it has to be said — it is not particularly impressive as far as sounding like real drums goes. As percussive sounds, however, they could undoubtedly have their place.

The auto-play/memory facilities are quite impressive: in the Normal Melody mode a composition of up to 400 notes and four-note polyphony can be recorded. To simplify things for the beginner, it is possible to enter the notes first without worrying about the rhythm of your playing, and then add the rhythm as a second stage operation. In practice it's very simple and effective. Then there's the three-channel Multi Memory, which allows a chord sequence plus two independent melodies to be recorded independently, again with aids to assist the beginner's technique. The chords are selected by depressing a key in the lower half of the keyboard that refers to the root of the chord and then depressing one of another 12 keys in the upper octave to determine whether it's a major or minor, etc. The possibilities extend to such complex chords as a minor seventh with a flattened fifth, which I found rather impressive, although I don't know how many people buying this keyboard would use it.

Strangely enough, no headphone output is to be found here, but a single built-in speaker allows low level practice and there is also a line output socket at the rear that allows you to connect the SK-1 to an external piece of equipment, whether for recording or amplification — and hopefully that will have a headphone socket.


£89 is very little, and you'll probably get it in the shops for even less than that; with that in mind the SK-1 is fantastic. But if you are seriously interested in musical sampling and the other features are of little interest to you, it will probably be rather frustrating to use. The Yamaha is around twice the price, and although the actual quality of the sampling isn't much better, it does offer a larger keyboard, eight seconds sample time and four-way multi-sampling, and thus is more flexible and musically useful. The SK-1 is great for playing around with and for adding bits and pieces to your tracks and live performances, but it can't be considered as a serious sampling proposition.

Casio SK-1 - RRP: £89

Also featuring gear in this article

Previous Article in this issue

Yamaha PYD 422

Next article in this issue

Mesa Boogie Studio .22

Publisher: International Musician & Recording World - Cover Publications Ltd, Northern & Shell Ltd.

The current copyright owner/s of this content may differ from the originally published copyright notice.
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International Musician - Nov 1986

Donated & scanned by: Mike Gorman

Gear in this article:

Keyboard - Home/Personal > Casio > SK-1

Review by Jim Betteridge

Previous article in this issue:

> Yamaha PYD 422

Next article in this issue:

> Mesa Boogie Studio .22

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