At a stroke, Kawai has attempted to combine the power and complexity of real-time additive synthesis with flexible multi-timbral capabilities. Will the combination set a new standard?

YOU, AND HUNDREDS like you, may not know it. But the lure of additive synthesis has always been strong for musicians interested in having complete control over the sounds they program - and aren't too bothered about how long it takes to exert that control.

Unlike their analogue brethren, whose "subtractive" control methods necessarily limit the type of timbres that can be created, digital additive synths give the programmer complete and utter control over the instruments' synthesised sounds. As a result, they can produce anything from realistic simulations of acoustic instruments to entirely synthetic timbres.

But this kind of power does not come without cost, and until recently, additive synthesisers have been prohibitively expensive to buy and incredibly tedious to program. In fact, very few of them have become readily available. Recently, a number of samplers have begun to include some basic "additive" options, but these have been very restricting and have required a significant amount of time to compute the resulting waveform.

Kawai's previous synth, the K3, also incorporates this basic type of additive synthesis. The machine's "user waveform" feature allows you to choose up to 32 of 128 possible harmonics, and set a relative amplitude level for each of them. But while you can create some interesting sounds with this method, you're limited to creating static waveforms, since there are no envelopes with which to change the level of harmonics over time.

With the new 16-voice K5, Kawai have made a quantum leap past the principle of the user waveform, and created an additive synthesiser. (Actually, the K5 does not conform exactly to the requirements for a truly additive synth, but we'll get to that later.) And in addition to being able to create its waveforms in real time, the K5 allows for very sophisticated control over them.

Additive Synthesis

WORKING UNDER THE assumption that not everyone is familiar with this method of synthesis, it's worth spending some time examining how it works and the theory behind it. The owner's manual which comes with the K5 doesn't offer much help here. In general, its explanations of what specific functions and the overall instrument can do seem incomplete, which is unfortunate, to say the least.

Additive synthesis is based on the principle that every sound imaginable can be broken down into (and hence recreated with) a group of sine waves. The sine wave is the simplest and purest waveform possible, containing no overtones besides the fundamental frequency. Each sine wave within a complex sound is referred to as a harmonic or a partial of the sound. Different partials occur at different frequencies, and the ratio of these frequencies to the first partial (the fundamental), as well as the relative amplitude and change in amplitude of each partial determines the harmonic structure and, consequently, the timbre of different sounds.

Additive synthesisers work by allowing the user to select the partials that are to be incorporated into the sound, and then to program their initial frequencies, their relative amplitudes and the envelopes which determine how these components change over time. The three-dimensional waveform displays, or FFT analyses, that many sample editing programs (such as Digidesign's Sound Designer) can produce are excellent examples of this principle. Each of the individual waveforms which make up the total display represents the amplitude envelope of a particular harmonic (or, in the case of Digidesign's SoftSynth, a particular overtone) is actually a sine wave at a particular frequency with a particular amplitude envelope.

The K5's implementation of additive synthesis is quite sophisticated but, as mentioned above, it does not fulfil all of the "classic" requirements for a truly additive synth. Specifically, there are no individual pitch envelopes for each partial, and there are only eight possible amplitude envelopes to choose from. In addition, only whole number partials - which make up the natural harmonic series - can be used, since inharmonic partials are not directly available. (Inharmonic partials are "out of tune" with the natural harmonic series and often provide the "noise" content of many sounds.)

While having so few envelopes may appear to be a serious limitation, this turns out not to be the case in practice. In fact, you'll probably find, as I did, that with the huge number of parameters already available on the K5, the limited number of envelopes reduces the tedium of programming sounds, without really reducing the flexibility of the instrument.

The first thing you notice about the K5 - or the modular version, the K5m - is its large, informative liquid crystal display. As we'll soon see, it's this display that really saves the instrument from being a programmer's nightmare.

Any of the machine's 48 internal single patches or 48 internal multi patches - or an equivalent number from the slim, external RAM or ROM cards - can be accessed by hitting one of the four bank groups and then one of the 12 individual buttons.

The LCD, which has an adjustable contrast control for easy viewing at nearly any angle, displays the patch's name and location and, for single patches, the assignments for the pedal controller and mod wheel. This last feature can be very handy if you're prone to forgetting what the controller assignments are for various patches.

Hitting the Edit button brings you to the basic edit page. From here, 12 individual buttons provide quick access to various functions. Thankfully, Kawai have avoided multifunction editing controls for single patches, so you can easily keep track of where you are during the editing process.

"The process of waveform creation requires that you set a basic level for each of the 63 harmonics in a source, and then assign them to one of four six-stage amplitude envelopes."

To move around within any of the 13 pages available, you make use of the four cursor buttons, and to change the value of parameters you use the now familiar increment dial. The system is simple, logical and, once you get used to it, very fast.

Voice Architecture

TWO TYPES OF patches are available on the K5, "single" and "multi". Multi patches (which will be discussed further on) are flexible combinations of single patches - much like performance memories on other synths. Single patches consist of two "sources," each of which contains a Digital Frequency Generator (DFG), a Digital Harmonic Generator (DHG), a Digital Dynamic Filter (DDF), and a Digital Dynamic Amplifier (DDA). In addition, each source can have its own Keyboard Scaling curve, and the combined sources share a programmable LFO and a Digital Formant Filter (DFT), which basically works as an 11-band - one band per octave - graphic equaliser.

The sources can be combined either in series, which Kawai call "full mode," or in parallel, which is termed "twin mode". In full mode, the K5 gives you control over a whopping 126 harmonics at once - that is, 126 sine wave oscillators. In twin mode, there are two sets of 63 which can be detuned against each other.

A quick run through the instrument's presets led to the discovery that nearly every one used twin mode because, except in a very low range, harmonics above the first 63 are inaudible.

Despite the "additive" title, Kawai's new synth maintains a sense of continuity with traditional analogue, subtractive synths. In fact, and this is strange, the best way of understanding the K5 voice architecture is to think of it in relation to a subtractive synth.

The "oscillator" of the K5 is a combination of the Digital Frequency Generator and the Digital Harmonic Generator. The DHG determines the harmonic spectrum - the basic "shape" of the initial waveform (s) - via the amplitudes and envelopes of the various harmonics, while the DFG controls their pitch. The DDF and DDA function as sophisticated versions of their analogue counterparts, and the DFT offers a final degree of control over the sound.

The real heart of the K5, and the only "additive" portion of the synth, is the DHG. To continue the analogy, think of each source in the DHG as a sophisticated, programmable "waveform select" portion of the "oscillator". Because you can create your own waveforms, however, the number of available choices is unlimited. You can program traditional analogue-type waveforms, very close imitations of acoustic instrument sample loops, or whatever it is that you desire.

The instrument's single patch presets give you a fairly good idea of the possibilities, though they're not as effective as they could be. Sample-quality pianos, warm strings, clangy chimes, drawbar organ and many other basic waveforms are present. The sounds are generally sharp and clear, with a touch of high-end digital bite.

The actual process of waveform creation requires that you set a basic level (0-99) for each of the 63 harmonics in a source, and then assign them to one of four six-stage amplitude envelopes.

In addition, each harmonic can be affected by two types of modulation. The first of these is a traditional LFO-type modulation which Kawai calls "effect". Each envelope group - that is, all the harmonics assigned to a particular envelope - can have a separate modulation rate for this effect, which is the only control you have over it.

The other type of modulation, which can be turned on and off for each harmonic, is a composite modulation buss that determines how much effect the amplitude envelopes have on the various harmonics they are assigned to - in other words, the envelope modulation amount. Attack velocity, aftertouch, keyboard scaling and the LFO can all affect the amount to produce a complex variation of the basic envelope. With a bit of planning - working out which harmonics you want to be affected and how you want them to be affected - this modulation buss can effectively double the number of envelopes available.

The DFG sets the basic pitch of each source (tunable over four octaves) and has a dedicated six-stage pitch envelope that can be modified by velocity, aftertouch and the LFO. In addition to creating some nice detuned chorus effects, the wide tuning range of the DFG allows the K5 indirect access to inharmonic partials.

"Despite the 'additive' title, Kawai's new synth maintains a sense of continuity with analogue synths; the voice architecture is best understood in relation to a subtractive synth."

Probably the most unfortunate limitation of the entire instrument is the K5's inability to access inharmonic partials directly, because almost all natural sounds have at least a few non-harmonic or inharmonic partials. But by detuning one of the sources against the other in either twin mode or full mode, you can create partials which lie between the whole numbered partials of the harmonic series. It takes a good understanding of harmonic theory and a bit of arithmetic to figure out, but it is possible. And that's a statement that's pretty much true of the K5 in general.

Editing

OK. LETS TALK about how sounds are put together. The monotony of programming additive synthesisers has always been - and will continue to be - their greatest shortcoming.

The amount of information that needs to be entered is generally much greater than it is for any other synthesiser - simply because there are more variables to be chosen. Consequently, it's harder to keep track of where you are, and it also takes more time to achieve the desired result. To add further to the problem, most of these instruments require a certain amount of time to calculate the new waveform after each bit of editing.

Kawai are obviously aware of all this, and have taken it into consideration when designing the K5. For here, at last, is an additive synthesis machine that incorporates several functions which allow programming to be accomplished quickly, as well as effectively.

Greatly contributing to this efficiency is, as we've said, the large LCD, which is capable of displaying a great amount of information at once. Despite its potential benefits, however, the K5's display isn't used to its greatest advantage, simply because it shows only envelope parameter values, rather than resulting envelope shapes. This seems rather odd, especially when you consider that the response curve on the DFT (which can be displayed) is quite similar to an envelope.

In addition to the display, though, the real-time action of the K5's DHG is a great boon that hugely eases the programming process.

Another function which helps simplify programming is the Copy feature on the basic edit page. This function allows you to make a duplicate of any part of a source, or even an entire source, and then store the copy in any location. It is particularly handy if you want to make subtle alterations to one of the harmonic spectra (created by the DHG) that you've programmed for a patch.

The most well thought-out section of the whole machine, however, is the DHG page. As mentioned above, the options offered by the digital harmonic generator are what give the K5 its unique character, so it's encouraging to see that Kawai have taken the time to make it easy to understand and use.

The key to the success of this page lies in the grouping functions, which allow you to adjust the levels of an entire group of harmonics in a number of different ways at once. Most additive synths require you to set the level of each harmonic individually, which can be a horribly tedious process. With the K5, you can set the range of the harmonics you want to affect - signified on the LCD by a solid bar under the ones specified - and then choose whether you want to further affect harmonics that already have a non-zero amplitude (referred to as "live") or ones within that range that don't have any amplitude yet (very oddly termed "die"), or finally, all the harmonics within that range. In addition, you can decide if you want to adjust only odd harmonics, even harmonics, octave-related harmonics or fifth-related harmonics.

Once you've chosen the harmonics you want to affect as a group, you can then select the angle at which the levels will increase. They can be increased evenly, with a high-end roll-off or a low-end roll-off. One option that isn't available is a logarithmic increase or decrease, which would have been helpful in producing sawtooth-type waves, but these grouping options are still an enormous improvement over most other systems.

One other point that deserves mention is that Kawai have included the ability to turn off various modulations and components of each patch (like the DDF and the DDA) so that you can determine the effect they have on the overall sound. This can be very handy - not to mention educational.

Yet even with these helpful features, the K5 is not an easy instrument to program. It's by no means impossible, but it definitely requires some effort and some homework on the theory of sound. Kawai are aware of the difficulty involved and plan to support the K5 with a number of ROM cards - though let's hope the advent of these doesn't begin another DXesque preset mania.

"Even with some helpful grouping features, the K5 is not an easy instrument to program. It's not impossible, but it definitely requires some homework on the theory of sound."

Multi Patches

SINGLE PATCHES ON the K5 are capable of producing a wide variety of very big, impressive sounds on their own. But if you want an absolutely massive sound, up to 15 different single patches may be combined in one multi patch (check out the preset called "ALLOF'EM").

As mentioned above, multi patches are basically performance memories which allow you to create flexible splits (up to 15 at a time); layers (again, 15 at once across the entire length of the keyboard); velocity switches (up to eight different sounds per key); and combinations of all three.

That "multi-dimensional" subtitle at the start of this review stems from this useful voice assignment scheme. By the way, although the K5 is 16-voice multi-timbral, it can only play 15 different voices, apparently because of the limitations in the microprocessor.

As with the modulation facilities and grouping functions found in single patches, Kawai have managed to include some impressively flexible control options over the multi patches. They can be edited via five more dedicated software pages (Kawai use the term "windows" for multi patch editing) which allow you to set the zone of each single patch within a multi; its polyphony, which can be dynamically allocated; its mode - that is, whether it responds to the keyboard, MIDI or both; its MIDI channel, up to 15 MIDI channels at once for transmission and reception; its velocity switching range - in other words, at which velocity levels the patch will sound; its transposition, over a four-octave range; its fine tuning; its output level; and which of the four individual outputs its signal is to be routed to.

Most importantly, the K5 offers not only dynamic allocation of its voices, but also lets you choose either to give each patch a specific-number of voices, or to set it to "variable" so that it can have access to as many voices as possible. This feature, combined with the ability to assign each patch to its own MIDI channel, makes the K5 a formidable new tool for sequencing, especially if you take advantage of the four individual audio outs.

Each single patch within a multi patch an also have various MIDI commands (such as pitch-bend, aftertouch and so on, emanating either from the keyboard itself or from other MIDI controllers) individually enabled or disabled.

This leads us on to the MIDI implementation on the K5, which turns out to be very impressive. The two pages set aside for MIDI functions allow you to program some of the same functions found in the multi patch programs for the overall instrument.

These include setting the basic send and receive channel - which is separate from the individual channels set with multi patches - and enabling or disabling the optional hold pedal, expression pedal and foot controller, as well as portamento, program change (which can be set to affect single patches or multi patches, but not both), bend range, and tuning. In addition, the K5 can be set to receive or ignore pitch-bend, modulation, MIDI volume and attack velocity. The K5 keyboard also generates release velocity, though this data cannot be disabled.

The MIDI "basic" page also allows you to initiate System Exclusive dumps from the front panel, and enables reception of SysEx data. You can choose to send a single patch or an entire bank of patches in one simple operation.

Conclusions

WHATS THE SUM total of all this? Well, although the K5 and K5m are not truly additive synths, their hybrid additive/subtractive method of synthesis is a viable new alternative, and one that's capable of producing some impressive sounds. What's more, Kawai have included a number of features that offer you expressive control over those sounds. The complex modulation options and the ability to respond to release velocity, as well as other MIDI controllers, make the K5 and the corresponding module very playable instruments.

But for a synth to be a truly effective tool, you need to be able to create timbres of your own with it. Kawai have obviously spent a great deal of effort overcoming the problems normally associated with programming additive synths, yet although the friendly LCD makes the process as painless as possible, I suspect that, as with the DX7, a minority of dedicated programmers will produce most of the new patches.

Finally, though, it must be said that the multi patches turn the K5 and K5m from competent machines into absolute monsters. With a flexible dynamic allocation of 16 voices, four individual outputs and the ability to receive on up to 15 different MIDI channels at once, these instruments are a MIDI sequencer user's dream. The K5m, in particular, looks to be fine value for sequencing purposes, even in the light of competition from the likes of Ensoniq ESQ1 and Roland D50.

In the brief description at the beginning of this review, I questioned whether the K5 and K5m set a new standard. The obvious answer now is yes.

Prices K5. £1495. K5m. £1045. both including VAT

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