Korg Z1

Commercial physical modelling synths first appeared in 1994, but until now, nobody has produced one that offers truly multitimbral operation together with decent polyphonic performance. Korg's new Z1 does — and for well under £2000. In this, the first UK review of the finished instrument, Gordon Reid laughs wildly and plays lots of chords — because he can.

If you're one of those readers who skim‑reads the detail of a review, and then jumps to the conclusion and reads that in depth, please don't. Korg's latest hi‑tech keyboard is the world's first multi‑model, multitimbral physical modelling synth, and combines great strengths with the odd surprising weakness. It's a fascinating instrument, and it deserves some of your time. So, find somewhere comfortable where you aren't likely to be interrupted, take a deep breath, and join me for a thorough look at the Korg Z1.

The Basics

The Z1 is a bit of a hybrid. It lives in the case of Korg's flagship workstation, the Trinity, and incorporates a 61‑note keyboard that offers eight modes of aftertouch sensitivity, plus 13 modes of velocity sensitivity. Like the Trinity, it has effects, but as we shall see, they don't behave like the Trinity's. The heart of the Trinity's user interface, its touch‑sensitive screen, has also been replaced on the Z1 by a smaller 240x64 pixel LCD, but in exchange, 23 friendly knobs have sprouted from the Z1's upper panel (including, as on the Prophecy, five assignable Performance Editor knobs below the display). The Trinity's disk drive has also disappeared, but a rectangular touch‑sensitive X‑Y pad makes its appearance, and this fulfils many of the functions of the Prophecy's Log controller, which the Trinity also lacked.

Round the back, there are less holes than you might expect (more on this point later), with just a stereo pair of audio outs, inputs for volume, damper and two assignable pedals, plus the usual MIDI In, Out and Thru sockets. There's also a slot that accepts PCMCIA Flash ROMs and Flash EPROMs. The only other connector, apart from the power socket, is the headphone output located at the front beneath the control wheels.

Model Types

Like the Prophecy, the Z1 is a physical modelling synth derived from Korg's OASYS (Open Architecture Synthesis System), designed using the Synth‑Kit development system (for more on the development and architecture of the Prophecy, take a look at the original preview of the instrument in SOS May '95, and my subsequent full review in the October issue of the same year). The simplest way to approach the Z1 is to think of it as a 12‑voice polyphonic and 6‑part multitimbral Prophecy. This is an analogy that survives initial inspection, although it doesn't tell the whole story.

Like a Prophecy patch, a Z1 patch uses a pair of MOSS (Multi‑Oscillator Synthesis System) oscillators plus a sub‑oscillator and a noise source. Depending upon the type of model you choose to work with, you can hear the conventional outputs of each of these elements, or use the first oscillator and/or the sub‑oscillator and/or the noise generator to build sounds within the second oscillator (or vice‑versa). However, in addition to the nine model types offered by the Prophecy (the Standard Analogue model; VPM — for which read FM; the Brass model; the Reed model; the Plucked String model; the Comb Filter model; the Sync model; the Ring Modulator model; and the Cross‑Modulation model), the Z1 offers four new oscillator models, the additions being the Resonance oscillator, Organ model, Electric Piano model, and Bowed String model. Let's take a look at each of these oscillator models.

• STANDARD OSCILLATOR MODEL

The Standard oscillator is the one on which many players will concentrate. This offers sawtooth and pulse waveforms as the main oscillator outputs but, like some exotic polysynths, also allows you to add a triangle wave or sine wave, each with independent volume controls. You can apply Pulse Width Modulation to the sawtooth, pulse, and triangle waveforms. The mixed output then passes to a 'wave shaper' that further complicates the waveform to create harmonically complex, more interesting sounds.

• COMB FILTER & RESONANCE OSCILLATOR MODELS

Still in analogue‑emulation mode, we come to the next two oscillator types: the Comb Filter oscillator model and the Resonance oscillator model. A comb filter is so named because it introduces several tightly defined notches into any harmonically rich signal presented to its input, and its transfer function looks like the teeth of a comb. The Comb Filter Oscillator accepts seven different signals at its input (the 'other' MOSS oscillator plus noise; the sub‑oscillator plus noise; filter1 plus noise; filter2 plus noise; pulse noise; and an impulse) and, depending upon the characteristics of the filter, the output can vary from simple modulated noise to bright and complex tonal sounds. The Resonance Oscillator is similar, except that it takes the output from the 'other' MOSS oscillator, or the sub‑oscillator, or the noise generator, or filter1 or 2, and feeds them in parallel to four band‑pass filters. You can tune each of these filters independently, with individual gains and Qs. Passing noise through them generates a variety of haunting 'glassy' and spectral effects, and a flick through the factory sounds shows that Korg's programmers have found such effects to be this model's greatest attraction.

• RING MODULATOR, SYNC, & CROSS MODULATION OSCILLATOR MODELS

The next three models take the output (called, in these cases, the Modulator) from the 'other' MOSS oscillator, or the sub‑oscillator, the noise generator, filter1 or filter 2, and use it to modulate a Carrier generated within the model. The Carrier can itself assume four waveforms with various degrees of brightness and keyboard tracking, and the interactions between the Modulator and the Carrier provide a huge range of timbres, from smooth and melodic to screeching atonal excesses.

The Ring Modulator oscillator model is the first of this family, but it does not emulate analogue ring modulators. These output the sum and difference frequencies of two signals presented to their inputs, often resulting in clangorous, metallic‑sounding timbres. In contrast, the Ring Modulation oscillator model multiplies the Modulator and Carrier signals to generate a variety of ring modulation‑type effects. The Cross‑Modulation oscillator model differs from the previous model only in the mathematics of the interaction between the Carrier and the Modulator. In this case, the Modulator frequency‑modulates the Carrier, producing a form of 2‑operator FM synthesis, albeit with more modulation options than I care to count. This model generates strong, complex sounds, and is particularly suited to aggressive timbres.

The Sync Modulation oscillator model is the simplest of the Z1's oscillator models. Here, the Modulator re‑initialises the Carrier waveform each time it passes '0'. This is classic 'sync' (as found on many analogue instruments) but the effect on the Z1 is more subtle than on '70s synths, and the sounds are generally less aggressive than those obtained from the Ring Modulation and Cross‑Modulation oscillator models.

VPM is Korg's implementation of FM synthesis, although in some ways it is closer to Casio's Phase Modulation (as used in their CZ‑series of synths) than it is to true FM. There is only one Carrier and one Modulator per oscillator, but this Carrier may assume any one of four waveforms, and it is further 'wave‑shaped' before being modulated. I love VPM. The results are recognisably FM in nature, from classic DX7 pianos to bells and DX‑style basses, but they lack the background noise from which almost every FM synth suffered so badly.

• ORGAN MODEL

The Organ model offers three virtual drawbars per oscillator. Each of these drawbars may assume 16 pitches (of which nine equate to the drawbar footages of a Hammond) and four waveforms: SIN1 is a pure sine wave; SIN2 and SIN3 add the 2nd and 2nd+3rd harmonics respectively, and TRI is a triangle wave. You can add single‑trigger and multi‑trigger percussion with controllable delay to each drawbar. In a Z1 patch with both MOSS oscillators set to 'Organ', there are sufficient parameters to emulate almost any Hammond registration, but with a more limited amount of control. In particular, there's no way to build the patch so that you can push or pull every possible combination of drawbars.

• ELECTRIC PIANO MODEL

The Electric Piano model imitates a range of electric pianos by allowing you to adjust parameters relating to the shape and motion of a virtual hammer, the shape and size of a virtual tine, and the position of a virtual pickup. The results are superb, so I hope that Korg will release a 76‑note 'Z1 Pro' or even an 88‑note 'Z1 ProX'. If they did, the Fender Rhodes and Wurlitzer Programs would alone justify much of the Z1's price. Furthermore, you don't need two people to carry a Z1, and you don't have to tune it by soldering bits onto — or filing bits off — any tines. There's no contest.

• BRASS & REED MODELS

The Brass model is actually six models — Brass1, Brass2, Brass3, Horn1, Horn2, and ReedBrass — which represent various shapes and lengths of bore. Pressure and Character parameters then emulate the action of a player's lip position and tension, the shape and resonant character of the instrument's bell, and the presence of any mutes. The Reed model incorporates no fewer than 17 sub‑models (the Prophecy's offered a 'mere' 13) including a selection of saxophones, double reeds, a bassoon, a clarinet, flutes, harmonicas, and a 'reed‑synth'. In both models, the huge range of fundamental tones is further augmented by a noise generator, by a peaking EQ that adds overtones, and by dual pitch‑bend characteristics — smooth pitch changes as obtained by varying the bore length on a trombone, or abrupt, as obtained from an instrument of fixed length. The Reed model also offers a high‑pass EQ that removes low frequencies to provide a 'lighter' sound.

• PLUCKED & BOWED STRING MODELS

The final two models are the most complex. The Plucked String model simulates guitars, basses, Clavinets, harpsichords, and other, less well‑known stringed instruments. Its 'plucking' parameters represent the level, attack, and noise associated with the action, and the position at which the string is struck. The strings themselves are defined by their dispersions, damping, reflection characteristics, and the positions of their harmonics. Seven further parameters determine the position and nature of the pick‑up that detects the 'vibration'.

As expected, the guitars and basses are rich and authentic, but the real surprise is the even greater authenticity with which this model recreates the sounds of Hohner's classic Clavinets. Having owned and played D6s and E7s for too many years to admit, and having never found a synth that even came close, the Z1's Clavinet patches are a source of sheer delight.

Moving on, the Bowed String model emulates instruments such as violins and 'cellos, allowing you to define the bowing speed and the pressure with which the bow is dragged across the strings. 'Rosin' increases the friction between the bow and string (enhancing the tonal differences of different speeds and pressures) and damping parameters control the tonal characteristics of virtual 'fingering'. Parameters related to string position and dispersion characteristics imitate the playing of thin or thicker strings, and reflection parameters affect the ease with which notes sound. Finally, a peaking EQ accentuates or attenuates a range of frequencies to emulate various body cavities and sizes (the instrument's, that is, not yours!).

Programs & Multis

So, now you've mastered the Z1? Well, no... all we've described are the models that play a major part in replacing the oscillators on a conventional synth. These are but the first step to creating a patch (which Korg has, in time‑honoured fashion, called a Program).

The Z1 uses four sound sources in each Program. The modelled oscillators, OSC1 and OSC2, are the first and second of these and, except for the reed, brass, plucked and bowed string models (which require all the available DSP power for a single oscillator) you may allocate any MOSS model to either of them. The third is the sub‑oscillator. This offers sawtooth, square, triangle and sine waveforms, may be freely tuned with respect to OSC1 and OSC2, and can track the keyboard independently from them. The fourth and final Program sound source is the noise generator, which is a white source filtered by a dedicated resonant filter that can assume low‑pass, high‑pass, or band‑pass characteristics. You can toggle each Program sound source on and off using four dedicated buttons found alongside the real‑time controllers on the Z1's front panel, but, more usefully, you can use the Program's Mixer section to determine the amount that each will contribute to each of bus 1 and bus 2, which together make the final sound. The mixer also has a fifth pair of inputs, called Feedback, that allow you to feed the output from the Amplifier section back into the signal chain — though this needs to be used with care, otherwise all your careful programming will result only in distortion.

The mixed signal passes to a Filter Section that offers two multi‑mode filters, each of which can assume low‑pass, high‑pass, band‑pass, band‑reject, or dual band‑pass characteristics. The last of these is interesting because it emulates the formants of a human voice, and imitates the natural resonances of hollow bodies. You can route the signal through the filters in three ways: parallel, serial1 (in which only bus 1 is filtered) or serial2 (in which bus 2 ceases to exist and bus 1 is tapped both before and after filter1). Sounds complicated? It isn't, because the on‑screen graphics make everything clear. Both filters are resonant, will self‑oscillate, and their keyboard tracking is variable from ‑200% to +200%. Note, however, that a self‑oscillating digital filter needs to be 'kicked' into life, and selecting a Program with such settings will result in silence unless you excite the algorithm by playing a note.

The signal next passes to an Amplifier Section that boasts a dedicated 5‑stage envelope. But if one envelope appears a little mean, fear not. The dedicated EG Section offers four more of the same. The LFO Section is similarly equipped, with four LFOs, each of which can assume 17 different waveforms (including Sample & Hold). Each LFO may be independently sync'd to incoming MIDI Clock, and roughly 100 sync rates are available.

Other parameters include the scale type, of which there are nine presets and two user‑definable scales, and a Random Pitch Intensity parameter that introduces slight pitch instabilities to imitate analogue synthesizers (this is the direct equivalent to Roland's Analogue Feel parameter).

The Z1's effects section is made up of two Insert Effects (the imaginatively named Effect 1 and Effect 2), a Master Effects section (reverb and delay) and a simple 2‑band Master EQ, and these different sections lie in series on the stereo buss. In other words, everything passes through both effects; there's no assigning Effect 1 to one oscillator and Effect 2 to another, for example (more on this later). The two virtual Insert Effects units can each host one of the 15 Insert Effects, but DSP limitations mean that only Effect 1 can make use of all of the Insert Effects, while Effect 2 is constrained to the simpler algorithms. This brings me to one of my Z1 moans. The Korg Trinity grades its effects by size (1, 2 or 4 — a measure of the amount of DSP processing power each effect takes up) and allows you to select any of these up to a total size of four (eight in a multitimbral Combi). The Prophecy allows you to use six 'size 1' effects simultaneously — although the Prophecy manual doesn't actually use the term size. Nor does the Z1 manual, but doing a straight comparison of effect types from Trinity to Z1, I concluded that the total 'size' of the Z1's Insert Effects section is two; so, for example, you can't program an overdrive followed by a twin‑channel Leslie simulation, or chorus with multitap delay. Furthermore, the integrated modulators within the Insert Effects can't be synchronised with the main LFOs. But otherwise, and within these limitations, the Z1's effects are adequate.

You can assign the wheels, pad, switches and pedals to modulate various parameters. Furthermore, the five knobs in the Performance Editor section on the top panel can each control up to four parameters drawn from a list of 439 Program parameters, with the range and response curve independently specified for each. Any changes made using these knobs, even during live performance, can be saved as if they were full edits. Finally, while we're on the subject of controllers, these can be software re‑calibrated by the user. I've rarely seen this facility before (the Synclavier II has it) but it ensures that, in the absence of a major fault, different Z1s can always be calibrated to respond as you expect.

Once you've finished programming your, um... Program, you can allocate it to one of 18 Categories and 16 User Groups, and save it to any of the 256 memories arranged as two banks of 128 (see also the 'External Patch Storage' box). You can also combine up to six Programs, with individual note ranges, independent MIDI velocity ranges, and separate MIDI channels, into a multitimbral 'MultiSet'. Each Program can be assigned a different pitch and a different scale to its siblings, and their responses to MIDI controllers can also be defined, although only one Program can respond at any given time to the Z1's performance controls and editors. Effects can also be applied to a MultiSet, and this brings me to my second moan. In my Z1 preview two issues ago, I stated that the Z1's effects were multitimbral, as on the Trinity. It seems I was wrong, which is a real shame. A MultiSet's effects buss is identical to a Program's: in other words, it's a single stereo buss onto which two Insert effects, a Master effect, and an EQ are hung, and your entire MultiSet passes through all of this in series; there's no assigning of individual effects to individual Programs in the MultiSet.

While on the subject of patch architecture, I was slightly bothered by the speed (or, rather, the lack of it) at which the Z1 changes between Programs and between Multis. I suspect that, like some other DSP‑based devices, the Z1 generates a deafening digital click when on‑chip parameters are re‑initialised, so Korg has muted the outputs during a voice change. If you need to switch sounds while playing live, make sure that you have a couple of seconds to do so, because that's how long it takes.

Editing

Without the large display and touch‑sensitive interface offered by the Trinity, editing the Z1 could be a daunting task, especially since Korg have chosen not to give every parameter its own slider (as on the Roland JP8000) or its own knob (as on the Clavia Nord Lead). But that decision is hardly surprising — if they had attempted to do so, the top panel of the Z1 would have been the size of Wembley Stadium. So Korg have reached a compromise, by employing a two‑tiered editing system. (I always said that it would end in tiers!)

If you want to make simple edits in real time, 14 dedicated controls (known as the Real‑Time Controllers) make Minimoog‑esque editing simple and immediate. But if you want to get into serious sound synthesis, you need to burrow into Korg's new software interface. This, while not as marvellous as that employed by the Trinity, is decidedly superior to those employed by the Prophecy or any of Korg's other workstations. It works like this. You decide which aspect of the sound you wish to change, then press the appropriate button to access the right section within the programming system. Each section offers multiple pages that you can step through using the Page Left/Right buttons, and you can move between related parameters by pressing in one of the five Performance Editor knobs found below the screen. Once you have selected your parameter you turn the knob (or, if you prefer, use the cursor up/down buttons or enter the desired value using the numeric keypad) to make your edit. A range of graphics guide your decisions and, for many parameters, these show exactly what's happening whenever you have a twiddle.

If all this sounds a bit much for a few knobs and an LCD to handle, you can avail yourself of the excellent software editor that comes with the Z1 (see 'The Soft Option' box elsewhere in this article).

For all its power and seeming complexity, and its apparent desire to be all things to all players, the Z1 is easy to understand and use. Indeed, with fewer Program options than a Prophecy, and a better editing system, it's a programmer's delight. But don't let this penetrability fool you... the Z1 still offers more sound creation possibilities than are dreamed of in your philosophy, Horatio. There are, for example, 49 modulation sources that you can route to several squillion destinations, and most of the parameters within the modulation sources can themselves be modulated by any of the other modulation sources. With so much power at your fingertips, you'll be staggered that you can programme anything meaningful at all!

Reservations

There are a couple of areas, as I hinted at the start of this review, where I feel the design of the Z1 disappoints. Some of these are minor points that I've already dealt with, but there are a couple of others. Firstly, the 12‑voice polyphony. "But this is the first commercially available physical modelling instrument to offer so many voices," you cry. That's absolutely true; other modelling synths such as the Roland JP8000 and Yamaha AN1x offer only eight or 10 voices — but then these are only bi‑timbral, and don't offer piano and organ models, where you really need the extra notes, so the comparison is not valid. Fortunately, Korg's DSPB‑Z1 expansion board increases the Z1's polyphony to 18 voices, making pianos, organs, and MultiSets much more usable.

The DI‑TRI digital interface board is another upgrade that will soon be available. This adds a 48kHz wordclock input and an ADAT‑compatible digital output to the Z1, and it is this that brings me to my other major concern — the number of audio outputs.

A single pair of audio outputs is spartan provision for a 6‑part multitimbral synth and, contrary to expectations, the optional ADAT optical interface, although theoretically capable of providing up to eight channels of digital audio output, doesn't provide a remedy for this. The DI‑TRI only addresses four of the eight ADAT channels, and those are derived from the stereo buss. Channels 1 and 2 are tapped after the effects, and channels 3 and 4 are tapped before them; so you have no more control over your sounds' destinations than if you used the analogue outputs. This criticism would be ameliorated if the Z1's effects were multitimbral, but as already mentioned, they are not. Programs in MultiSets are mixed before the Insert Effects; so if your guitars are flanged (nice!), your Hammond organs are flanged too (not nice!). I'm surprised at this, and can't understand why Korg have done it. The Z1's basic voicing and editing features are superb, but the ancillary features are more limited than the other features would lead you to expect.

However, let's not get carried away. A Minimoog has limited envelopes and no memories, neither a Prophet 5 nor a Memorymoog are velocity‑ or aftertouch‑sensitive, and a Mellotron can only sustain a note for eight seconds. Yet we don't stand them against a wall and shoot them for crimes against synthesis. On the contrary, we revere them, because the sounds that they produce, the music that they inspire, transcends their technical limitations.

Furthermore, you have to consider what else is available in the Z1's league. You may like the sliders of the Roland JP8000, the knobs of the Clavia Nord Lead, or the colour of the Yamaha AN1x, but the JP8000 and AN1x are merely bi‑timbral, have lesser polyphony, also sport just two outputs, and have effects sections far more limited than the Z1's. They offer just one (analogue) model, and they are far less flexible or controllable than the Z1. The Nord Lead 2 (reviewed in last month's SOS) is better in this respect, with 4‑part multitimbrality and four outputs, but, like the Roland and Yamaha, it will only imitate analogue synths. Furthermore, these instruments have 4‑octave keyboards, so you'd never use them for complex piano or organ passages in the first place.

Conclusion

You could read sections of this review and conclude that I have come down hard on the Z1, but that would be a mistake. In the context of its competitors, it is well‑specified, and great value. Indeed, its analogue models alone justify much of its price, and if it had a 76‑note or 88‑note keyboard, it would be the world's best synthesized electric piano (see the 'I Have A Dream' box).

Most importantly, the Z1 passes the essential test: it makes me want to play. With Korg's permission, I took the pre‑release unit on the road, leaving both my Trinity Pro and my Wavestation at home. It was a tough test but, with the exception of a bug in the aftertouch software (which Korg assure me has already been put to rights by means of a swift software update), my Z1 came through with flying colours. The electric pianos and lead synth sounds were superb, and the Clavinet sounded as if I had a Hohner D6 tucked away out of sight; what I want (what I really, really want) is to carry on using them. Despite its one or two surprising design features, the Z1 is a remarkable instrument, and deserves every success.