When it was released 18 months ago, the Korg Wavestation stood out from the crowd. After several years of all-singing, all-dancing keyboard 'workstations', here was a dedicated synthesizer, trading the delights of the on-board sequencer, drum section and stock sampled sounds, for one of the most powerful methods of synthesis ever.

With its rich, evolving textures, the Wavestation's Advanced Vector synthesis was — and is — an ideal instrument for TV/film composers, and musicians working in less mainstream rock. However, lacking a selection of standard sampled instruments such as piano and drums, the Wavestation has less appeal for the average keyboard player.

The new Wavestation EX (reviewed last month) and Wavestation A/D (reviewed here) are essentially an attempt to appeal to the latter group, thanks to the addition of an extra 2MB of PCM waveforms — 516 waveforms instead of 364 — including sax, piano, guitar, and drum samples. (The piano and drum samples are similar to those on the Wavestation PCM/Performance ROM cards WSC-1 and 2). However, unlike the Wavestation EX, the rack mounting Wavestation A/D has several more features to recommend it.

Firstly, there's an extra internal RAM bank giving 200 Performances (50 more than the original), 140 Patches (35 more) and 128 Wave Sequences (32 more) with 2000 steps (500 more). [The additional Programme Card slot provides a further 50 Performances, 35 Patches and 32 Wave Sequences with 500 steps.]

Secondly, and uniquely, the Wavestation A/D provides two rear panel inputs so that the A/D's dual multi-effects processors are accessible to signals from external sources such as microphones, tape recorders, guitars etc. How many times have you wished you could use your synth's multi-FX on mixdown? Well, with the Wavestation A/D you can.

In addition, audio signals entering the external inputs can be processed by the A/D's amps, filters and vector mix envelope — just as if they were on-board waveforms. At its simplest, this provides MIDI gating of a stereo or mono audio source. At its most sophisticated, it allows a MIDI instrument such as a sampler to be completely integrated within the A/D's Advanced Vector synthesis, as we'll see later.

Finally, the extra eight multi-effects algorithms found on the Wavestation EX (or standard Wavestations fitted with version 3.0 software) are also available on the A/D, with the advantage that the external inputs can be used to provide carrier and/or excitation signals for the Vocoder effect.

AV SYNTHESIS

Korg have been making synths since the early 70s, when sounds were created by connecting discrete modules together with patch cables. Back then, a typical modular synth patch might consist of an oscillator (offering a palette of maybe five waveforms), a low-pass filter, an amplifier, plus two envelopes and maybe a couple of LFOs. This combination of modules exactly describes a single Wavestation voice (see Figure 1), except that the Wavestation A/D has 515 ROM waveforms — Korg call them Waves — to choose from! More are available via the PCM card slot, while Waves 516 and 517 bring the external inputs 1 and 2 in on the act.

All 516 Waves are listed in the excellent manuals. Many are sampled instruments of varying length, including single shot attacks and/or looped sustain portions. The remainder are short synthetic waveforms offering a diverse variety of harmonic content. All Waves sound great on their own, even before they pass through the Wavestation A/D's massive signal processing armoury! Waves 0 to 31 are reserved for Wave Sequences: special 'playlists' of internal PCM and/or card Waves, each featuring programmable duration and crossfade. More about Wave Sequencing later.

Waveforms (or Wave Sequences) are selected from the Waves page, where the structure of a Wavestation Patch is also determined. There are three structures available, using one, two or four oscillators — A, A & C or A, B, C & D — resulting in 32, 16 or 8-note polyphony respectively.

OSCILLATORS & LFOs

Each oscillator can be transposed independently over a range of two octaves, so with four oscillators per voice, layered and chord sounds are a cinch. Fine tuning of +/-100 cents is provided for detuning effects, while a Slope control allows tuning to be stepped in intervals of greater or less than than one semitone between adjacent keys. At the maximum positive setting, a one octave range covers two octaves, therefore 12 notes divide two octaves into 12 steps. This facility exists alongside special tunings (see 'Performance' below).

With a 2 or 4-oscillator structure, a Hard Sync function is available. This means that oscillator C (and B and D if all four are turned on) is synchronised to A: so whenever A starts a new cycle, all the other Waves start their cycles too. Since the periods of the slave oscillators differ from A's, the slave Waves are reshaped in sync with the master. The abrupt cut-off of the slave creates a new harmonically rich texture. It's the keyboard players' equivalent of the fuzz box, and hard sync sounds are great for lead lines.

As the 'Modulation Matrix' box shows, Oscillator Pitch is one of five parameters that may be modulated by any two of 13 modulation sources, including Envelope 1 which provides five Points (0 to 4, 3 being sustain, 4 being release), and four Times (rates) (see Figure 2).

All the modulation parameters are bipolar, that is they can produce a positive or negative effect. In addition, all five destinations can be modulated by any two sources simultaneously — an unusual and welcome degree of subtlety.

Though there are only five modulation destinations, most of the modulation sources can themselves be modulated! For example, the Depth and Rate parameters of both LFOs can be independently modified by any of the modulation sources listed in table one. Both LFOs allow you to control Rate, Initial Amount, Delay, Fade In and Synchronisation parameters. The latter starts the LFO on a positive phase, so that its effect will always begin from the same point each time a key is pressed. For example, if the LFO is modulating oscillator pitch, the initial pitch displacement will be the same for every new note when LFO Sync is on. LFO-Fade In gradually increases the LFO's modulation depth, producing a more natural effect when simulating vibrato. Each LFO offers Triangle, Square, Sawtooth, Ramp and Random waveforms — but no sine, an odd omission.

FILTERS AND AMPLIFIERS

The huge range of textures available from the waveforms in the Wavestation A/D's ROM, can be modified by filtering out harmonics with the 24dB per octave low pass filter. Unfortunately, no resonance (or 'Q') control is provided to emphasise a particular band of harmonics, which is a real shame. Used subtly, resonance can create a wide range of interesting textures. At extreme settings, resonance produces the kind Bleep And Booster sounds that the dance charts are currently full of. Without a resonance control, reducing the A/D's filter cut-off frequency usually sounds like simple attenuation rather than filtering (except on the most harmonically rich waveforms). Another disappointment is the filter's Exciter effect. Intended to brighten filtered waveforms, it seemed to make no difference at all.

The filter can be swept by any two of the 13 modulation sources including Envelope 1. Once again resonance is sorely missed, and modulating the filter cut-off sounds similar to amplitude modulation with many waveforms. Alongside numerical values, a graphic representation of the envelope appears on the Wavestation's large display — something you can expect on any instrument costing over £1000 these days. To make envelope programming easier, a set of predefined envelope shapes — such as 'piano', 'string' and 'organ' — can be recalled from a field called Macro.

Similar macros are available for the dedicated Amplifier Envelope, and both envelopes can be scaled by Keyboard Velocity and Note Number. Amplifier Output Level is one of the five modulation destinations, as are Mixer X and Y axes.

VECTOR SYNTHESIS

The X and Y axes pertain to a method of synthesis that made its debut over five years ago on Sequential Circuits' Prophet VS: Vector Synthesis. Despite the widespread critical acclaim that the VS attracted, by 1988 Sequential found themselves in deep financial trouble, largely due to problems with their Studio 440 drum machine/sequencer. An excellent 16-bit sampler (the Prophet 3000) arrived too late to forestall bankruptcy, enabling the massive Yamaha/Korg organisation to purchase all Sequential's technology at a knock-down price. Fortunately, the Japanese giant retained a Californian base and re-employed many of Sequential's R&D staff. The first fruits of the new relationship were Yamaha's SY22 and the original Korg Wavestation — both Vector-inspired synths.

Vector Synthesis provides a way of dynamically varying the balance between two or four oscillators. Like the original Prophet VS, the Wavestation has a front panel joystick with which to change the A/B/C/D oscillator mix. With the joystick fully left, 100% of oscillator A is heard. When fully right only B is audible. Fully up gives C only, and fully down is D only. In the centre position, you hear 25% level of each oscillator.

Different textures can be created from the same four oscillators by setting the joystick to different positions, and a Patch may consist of such a static blend. Dynamic variation of the A/B/C/D oscillator mix is controlled by a 4-stage envelope similar to Envelope 1 (see Figure 2). Each point in the Mix Envelope represents a specific balance of the Wavestation A/D's four oscillators which is set using the front panel joystick. On the Edit Mix Envelope page, the level of oscillators A, B, C and D are displayed as percentage levels for each Point. A graphic (similar to that shown in Figure 3) illustrates the path the joystick would need to follow to move from one point — one mix — to the next. The Mix Envelope's four Time parameters set the rate at which one mix changes to another.

By programming Point 1 with 100% of oscillator A, Point 2 with 100% of oscillator B and so forth, a composite sound can be constructed from individual samples. Many lower numbered ROM Waves are stored as constituent parts for just this purpose. For example, the Electric Piano offers Keythump, Body 1 And Body 2 sections. Stepping swiftly between unrelated Waves produces predictably quirky results. With longer Time settings 'evolving' sounds can be produced. Crossmixing Waves of similar tone produces textures with subtle tonal shifts. More subtle variation in a sound can also be produced by programming less dramatic mix changes with the joystick. (It would be great if the Wavestation A/D had macros for Vector mix envelopes.)

Oscillator pitch is another parameter to investigate in the context of Vector synthesis, since by setting each oscillator to a different pitch, the mix envelope can be used to play four distinct notes (or chords). With fast time settings, this produces an arpeggio effect, while slower times create sounds with crossfading pitch changes — absolutely brilliant stuff.

The mix at Point 3 remains constant (sustains) until a key is released. However, yet more movement can be added by setting Points 0-3, 1-3 or 2-3 to loop forwards (or forwards and backwards) once the sustain point is reached. Loops can repeat from 1 to 126 times, or indefinitely. As if this isn't enough, you'll recall that Mixer X and Y axis are two of the five modulation destinations, so LFOs, velocity and external MIDI controllers etc. can all dynamically control the A/B/C/D oscillator mix. The mix programmed for point 4 is only heard when a key is released, (providing the amplifier has a reasonable length Time 4 value).

USING THE INPUTS

The Waves for oscillators A, B, C and D can be selected from within the Edit Mix Envelope page. Waves 516 and 517 route audio Inputs 1 and 2 directly into a voice, making it possible to process any audio source through the Wavestation A/D's filters, amplifiers, vector mixer and digital multi-FX processors (see Figure 3).

A continuous source of audio entering Inputs 1 and/or 2 (I tried a cassette player) can be gated by sending Note On/Off events from a MIDI controller connected to the Wavestation A/D's MIDI In. The attack/release times of this MIDI gate can be changed by editing the dedicated amplifier envelope, and by splitting the feed to the A/D inputs specific audio events can be anticipated. When connecting a MIDI instrument such as a sampler or synth, no anticipation is required since both the instrument and the A/D receive a common Note On/Off trigger when the instrument's MIDI out connected to the A/D as in Figure 4.

The volume and tone of an audio input can be affected by editing/modulating the amplifier and filter — producing tremolo and 'wah' effects respectively. Using the LFO's random waveform to modulate to filter cut-off, stepped tonal changes can be produced; modulating the filter cut-off via keyboard position makes this effect even more controllable. Playing more notes also increases the volume of the audio coming in via the audio inputs.

Using the Vector Mix Envelope, it's possible to set up a Patch that dynamically blends internal sounds with external audio. Thus any MIDI instrument can become a vector synth, and any sound or music you beg, borrow, steal or make can be manipulated to within an inch of its life. I had a lot of fun MIDI gating old telephone answering machine tapes and creating vector synth patches incorporating ambient music. Using a MIDI sampler with the A/D is particularly effective, giving the A/D access to a of new library of Waves — the equivalent of a mountain of Wavestation PCM library cards. Many other possibilities spring to mind, particularly when multitrack recording/MIDI sequencing, since A/D inputs can be gated/manipulated in sync with other audio/MIDI tracks — remix engineers take note!

PANNING

As you can see from Figure 3, audio passes through a Panning stage after the Vector mixer. How panning affects a Patch's oscillators, depends on a Patch's output routing. Each oscillator can be assigned to one or more of the four FX Buses (A, B, C and D). These lead to the four audio outputs 1/L, 2/R, 3 and 4 via the dual Multi Effects Processors (see Figures 5 and 6).

With oscillators A and C (and/or B and D) assigned to Bus A and B (and/or C and D) respectively, the image integrity of a stereo audio at Inputs 1 and 2 can be maintained. However, if you like, you can manipulate the pan position of an audio input with Velocity or Keyboard Note Number.

If oscillators A and C (and/or B and D) are assigned to identical Waves/Inputs and assigned to Buses A and C (and/or B and D), moving the joystick or programming a Vector Mix Envelope makes the sound travel across the stereo image. This is because the volume of Wave/Input X is increasing while the volume of Wave/Input Y is decreasing.

If each Wave/Input is set to a unique effects Bus, (ie. oscillators A, B, C and D are routed to FX Buses A, B, C and D), the vector mix envelope/joystick can control two stereo mixes simultaneously — 1/L and 2/R, plus 3 and 4. With oscillators A, B, C and D assigned to the same Wave/Input, the Wavestation A/D offers 4-channel panning. Film and TV engineers/composers will no doubt appreciate the possibilities that this offers when mixing for 3 and 4-channel systems such as Dolby Surround/Stereo/SR-D, Kodak Cinema Digital Surround.

EFFECTS

The A/D is the first synth to provide external access to its Effects section, a facility useful at mixdown, or for those on a tight budget. There are two fully independent Effects Processors — FX1 and FX2 — that can be can be arranged in series or parallel, as Figures 5 and 6 illustrate. The two configurations offer a choice between treating Waves/Inputs with two independent stereo effects, or giving two sets of Waves/Inputs independent stereo treatment. As most Effects programs offer between two and six simultaneous effects, parallel routing is generally more useful. The amount that Buses C and D contribute to the L/R mix can be modulated in both series or parallel configurations.

On mixdown, parallel routing means that the a 2-oscillator Patch can be effected by FX1 (emerging at outputs 1/L and 2/R), while audio inputs 1 and 2 are routed to FX2, (emerging at outputs 3/4). Thus the Wavestation A/D can be an independent synth and an effects unit simultaneously — revolutionary stuff!

Ensoniq were the first synth manufacturer to offer integrated built-in digital FX, that is, allowing effects parameters to be modulated from synth and performance controllers. Each Wavestation A/D digital effect offers at least one parameter that can be modulated from various sources including MIDI controllers and the front panel joystick.

There isn't space to describe all 55 effects (see list), but all are on par with those found in the current crop of dedicated units costing around £300-400. Both the Phasing and Flanging effects are worth mentioning as each has a warmth and depth not normally associated with digital devices. The Harmonic Chorus is interesting, and the Rotary Speaker outstanding. Like the Wavestation EX (and standard Wavestations fitted with version 3.0 software), the A/D offers seven new effects algorithms — Stereo Compressor + Limiter/Gate, Small Vocoder 1-4 and Stereo Vocoder + Delay 1-2. Of these the Vocoders are the most interesting.

A vocoder has two inputs — one for audio (the carrier) and another for a control signal (the modulator). The control signal superimposes its spectrum on the audio signal, so if the control signal is a voice, the audio appears to be talking. Another way of thinking of it is to imagine a graphic equaliser's sliders automatically responding to match the spectrum of the control signal. 'Talking' instruments are very much a vocoder's forte, but there are plenty of other possibilities. For example, using a drum machine as a control signal, the tone of a harmonically rich pad changes in sympathy with the rhythm. With the Wavestation A/D, both Waves and audio inputs can be used as either audio and control signal sources (via Buses A to D). Thus a ROM Wave can control the spectrum of an an audio input and vice versa.

WAVE SEQUENCING

The control signal for a Vocoder should be a sound with dramatic variations in tone, thus the human voice and drum machines make ideal control sources, as mentioned earlier. Sounds with wide tonal variations can be constructed fairly easily using Vector synthesis, but the Wavestation A/D offers another, even more powerful way to construct sounds — Wave Sequencing.

A Wave Sequence is exactly that — a sequence of up to 500 ROM Waves (or signals from inputs 1 and 2) playing through from start to finish. Level, course and fine Tuning, Duration (up to 10 seconds) and Crossfade are programmable per step, and the entire sequence can be looped up to 126 times, or indefinitely. Thus it's possible to programme tunes or drum riffs. Whereas sampled riffs change tempo across the keyboard, Wave Sequences remain at a constant tempo even though the pitch (and sample length) of individual Waves (within a sequence) alters.

The stepped and cross-faded sounds that Vector Synthesis produces (as described earlier) can be created with Wave Sequencing too, with the added attraction that there are up to 500 steps to programme rather than just four. Another big advantage is that Wave Sequences can be synchronised to MIDI clocks: how about using a complex MIDI synchronised Wave Sequence as a Vocoder excitation signal...

Programming Wave Sequences is fairly straightforward, though hardly intuitive. Each sequence step and its parameters are displayed in a list. Selecting Waves/Inputs and editing parameters is done by hopping around the screen with the cursor. This is fine for an 8-step sequence, but when dealing with more complex sequences, life suddenly becomes extremely frustrating (especially in £1,000 per day recording studios). Ideally, it would be possible to map a collection of Waves/Inputs on to the keyboard and play them whilst listening to a metronome.

PERFORMANCE

The sonic possibilities of Wavestation A/D really boggle the mind. Remember that a Wave Sequence is only one of four audio sources (Waves or Inputs) per voice. The Waves/Inputs/Wave Sequences may or may not be treated by filters, amplifiers and modifiers, or cross-faded/panned with Vector synthesis. And this is only at Patch level. Up to eight Patches can be combined in velocity-controlled layers or splits to form a Performance — the front panel selection level. Each Patch within a Performance (a part) can be independently Transposed, Key On Delayed, Detuned and even set to play one of 12 key scales (Pythagorean, Werkmaster III, Kirnberger III et al). Parts may then be treated with the dual Effects Processors. There are 16 MultiMode setups, which assign a Performance to each MIDI channel.

With all these possibilities, many Wavestation A/D Performances sound like mini-demo tunes rather than just individual instruments. Performances like 'Northan Lights' begin with dreamy pads that constantly shift in tone and pitch, then suddenly in comes a little downward sparkle like a passing meteor. 'A Touch Of Rain' offers stacked piano and stereo strings, with the lower octaves offering an additional drum riff behind which wind, rain and chimes continually cross-fade. Just add film: nature, horror, sci-fi — it's all here. For TV, many Wavestation Performances could easily be station idents or arts show theme tunes without modification. And all are available at the touch of a button.

And there's the rub. Programming. Many musicians/composers may never edit beyond Performance level (stacking Patches), yet here is a synth you have to programme in order to get anything other than (admittedly stunning) presets, many of which have already graced innumerable films, commercials and documentaries.

So is the Wavestation A/D easy to programme? Well, the large display/soft key approach is infinitely better than a one-line LCD, though the machine's habit of cutting off notes whenever a parameter is edited is infuriating; you have to constantly retrigger a sound. This, and the single data entry wheel, makes programming feel like painting a canvas through a wire mesh — possible but awkward. Still, apart from the extremely knobby JD800, every other synth on the market has the same problem.

The new ROM Waves (mainly pianos, basses and drums), though great, simply aren't enough to persuade a potential Proteus or M1 owner to go the Wavestation route (see Wavestation EX review in last month's SOS). However, for musicians, producers and composers who need to create unusual instruments and textural atmospheres, the Wavestation A/D offers unparalleled possibilities as I hope this review has suggested.

Further information

Wavestation A/D £1,450 inc VAT.
Wavestation EX £1,499 inc VAT.
Wavestation (V3 software) £1,350 inc VAT.
EXK-W (Wavestation to EX upgrade kit) £414.18 inc VAT.
V3 Software update free.

Korg UK, (Contact Details).