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Organ Synthesiser Module

Another contender for the recently-reinstated Hammond Drawbar crown comes in a single rack space. Gordon Reid organises his thoughts.

In spite of advances in digital technology, the sound of the tonewheel Hammond organ remains unmatched - the latest pretender to its crown is Voce's DMI64.

IF THE PIANO is the most flexible keyboard instrument yet invented, the organ must surely come a close second. Even today, across a wide variety of musical styles, an old Hammond tonewheel or Vox Continental can often be found lurking somewhere in the mix. Many attempts have been made to copy the genuine organ sound - most notably in the 70s by companies such as Korg, Roland and Crumar - some of whose instruments are still highly sought after.

Where original Vox organs are relatively light and compact, and can be found at modest secondhand prices, however, Hammonds are invariably large and weighty - consequently, you're more likely to want a Hammond impersonation than the real thing. To date, most desirable of the "mock" Hammonds are the Korg CX3 and (in particular) BX3 which, in most players' views, came closest to the sound of the original. Although the BX3 is no half-ton, un-split monstrosity requiring four roadies and a reinforced stage, it's no lightweight either. And the BX3 is not only big, it's also rare, so if you want that genuine "C3 played through a Leslie 122" sound, you have to play a Hammond C3 through a Leslie 122. Unfortunately, amateur bands can rarely afford the road-crew or the transportation costs of lugging a real Hammond around and, unlike the piano (which can now be replaced for most purposes) there's no substitute for the real organ thang. Until now...

The Voce DMI64 Mark II (catchy name) is a 1U-high, rackmounting digital synthesiser designed specifically for emulating organ sounds. Finished in a distinctive silky grey, it sports a mere four push button controls, a four-character LCD window, an LED, an on/off switch and, on the back panel, two audio outputs, MIDI In, Out and Thru, and a socket for the external power supply. Regardless of its visual simplicity (or perhaps, because of it), the DMI is one of the most attractive rackmount devices I've seen in a long while. Internal construction is also excellent with every component except the operating system ROM mounted directly onto the single circuit board. The ROM is socketed, implying the possibility of future upgrades. A lithium battery provides the voltage for the internal memories and is expected to last for four years, but if it's removed from its clip or otherwise disconnected the DMI reverts to the factory presets.

Three other items come with the DMI: an external nine-volt transformer, an IBM-format floppy disk containing the DMI editor/librarian, and a manual. Maybe because the DMI is so simple to understand and operate, the unthinkable has happened - I'm not going to slate the manual. It is brief but comprehensive and, although a little "techy" in places, should present few problems. Two appendices contain a listing of the factory presets, plus an explanation of the synth's MIDI SysEx dump format. Not bad.

Using the Voce as a preset box couldn't be simpler. Plug in the power, plug in the MIDI, plug in the audio, and plug in the talent. The single LED glows green to show that the power is switched on, and flickers red when MIDI data is received. (If you're using a controller with active sensing, the LED goes greenredgreenred.) The LCD shows the patch number allocated to the basic MIDI channel, and this can be changed using the Up/Down Preset/Parameter buttons. Patch changes can also be received from the controller keyboard. There are six audio assignment modes available. These are: channel 1 only, channel 2 only, mono (channels 1 & 2 identically), stereo (which can be used with the onboard effects to give a more spacious sound), split, and multitimbral. Polyphony is a stunning 64 notes, so those of you brought up on Emerson-style wrist-and-forearm block chords won't be disappointed. The Split function allows you to select two patches (one to play above, the other below, a user-defined split point), and thus imitates dual manuals from a single master keyboard. The DMI can then be forced (using 16 MIDI channels) into playing 32 different patches simultaneously - all at different volumes and at different pitches if required. This enables the Voce to imitate the most complex organs - right down to the registration and coupling of each manual.


THE VOICING ON the Voce simulates the drawbars on a traditional organ. Each waveform is described in terms of footages from 16' up to 1', and by drawbar extensions. Thus waveform 01 ('Church Ham') is shown as 848848448 - a neat and obvious notation if you're au-fait with the real thing. There are 64 waveforms in the DMI and these can be freely assigned within the 100 programmable patches (which Voce confusingly call presets). Presets 00-07, then, are Hammond samples. The thinner, more cutting tones of a Vox are represented in numbers 08-15. Frf (Farfisas?) appear in 16-23. Then, following a strange selection of somewhat unorgan-like tones, there are a further selection of Hammonds in 33-56. Despite digital oscillators, the tones are warm, if a little clinical, with just a touch of movement even when all the effects are set to zero. The output rate of the waveforms is 48kHz, the waveforms are 512-point, 22-bit samples (only 10.4 milliseconds long but very high resolution), and the noise floor is -70dB, so in theory the voice quality should be equal to that of, say, an Akai S1000.

The Voce also offers 64 percussion waveforms. These vary from simple clicks, through monotones, to complex multiple-footage waveforms. Checking closely, you'll find that the percussion waveforms are identical to the voices - it's just that they decay rather than sustain indefinitely. Three parameters control the percussion: waveform, volume, and the duration of the decay. Two different percussion patches (notionally called on and off) can be allocated per patch, offering two different percussion sounds for a single voice.

"Polyphony is a stunning 64 voices, so those brought up on Emerson-style wrist-and-forearm block chords won't be disappointed."


UNFORTUNATELY, EDIT MODE on the DMI is the ultimate nightmare creation of the programmer. The range of parameters available is extensive - waveforms, effects, MIDI control and mapping, pitch, volume, channel splits and assignments, SysEx, and multitimbral assignments - but these are all selected using just the two parameter Up/Down buttons, following which the value is modified using just the two value Up/Down buttons. Hence, only four buttons - it's compact, but positively tedious. When compared to a fistful of drawbars, the Voce is a dog to edit. Worse, there's no edit buffer, so any changes made to the patches are destructive - they're stored directly in patch memory.

The Leslie speaker creates its unique sound by passing the output of two stationary speakers through revolving rotors. The bass (anything below 800Hz) plays downwards into a single rotating horn, while the treble plays upwards into what looks like two rotating horns (although one of these is a dummy, provided to stop the whole assembly from shaking itself to bits). Each rotor assembly has two rotation speeds - slow for chorus effects, and fast for tremolo. The result is a sound that combines the Doppler effect (sinusoidal pitch shift) with phase shifting, timbral modulation, and amplitude modulation. This makes the Leslie extremely difficult to emulate. Electronic effects usually employ a modulated chorus to give movement to the (essentially) tame organ sound, but this doesn't come close to the sound of a Leslie. Voce have used a chorused pitch modulation for their effect, taking account of the Doppler effect caused by the rotors' rotation, but have largely overlooked the other consequences of the rotors. (Don Leslie was recently quoted saying "Everybody describes the Leslie effect as the Doppler effect, but they don't really understand what it's doing".) The DMI effect has four parameters - acceleration and deceleration rate (0-100), and fastest and slowest velocities (0-20), but applies only one rotation rate to the whole frequency spectrum. A real Leslie uses two rotation speeds simultaneously - one for the treble, and one for the bass - and these are rarely (if ever) the same. Consequently, the Voce rotating speaker simulation is disappointing.

Vibrato and chorusing are also important consequences of a Leslie's rotation, and players often use pedals to recreate them on non-Leslie'd organs. This makes them integral components of the classic organ sound. The DMI offers both chorus and vibrato with five parameters for each: initial amount and speed when "off"; amount and speed when the effect is "on"; and four depths of effect (0-3). Twenty-one speeds are available (0-20) but there is no acceleration or deceleration. The instantaneous transition between speeds can be disconcerting, but is no more of a problem than using an external effect unit. The pitch-shifting LFO is roughly sinusoidal at low speeds giving a smooth chorus or vibrato, but at higher speeds (15+) it begins to sound like a square LFO modulating the oscillator pitch. Mixed with external effects such as delay and reverb this is not much of a problem, but in isolation it's not very pleasant at all.

For yer actual Hammond impersonation you gotta have grit, bite and guts. Distortion occurs throughout the sound generation of an organ - dirty tonewheels, ageing amps, overdriven Leslies and, of course, dozens of valves adding their characteristic buzz to the sound - so no organ synthesiser should be without an onboard overdrive. The DMI has one, but it is another source of disappointment. A single distortion circuit is provided, but this can only be switched on or off. Worse, it's applied to the entire audio output whether the DMI is being played for a single patch, or in 32-patch multitimbral mode. It's not even as if it's a good overdrive. It has the fizzy, annoying character that guitarists spend hundreds of pounds avoiding. I switched the distortion off and played the Voce through a Roland GS6. The GS adds warmth where the onboard effect adds fizz, and at high volumes and pitches the GS tries to scream like a genuine Hammond. In contrast, the Voce distortion grates like a rusty moped.


THE 5.25" IBM-FORMAT diskette supplied with the DMI contains a public domain editor/librarian. Since very few UK musicians have a DOS-based PC with MIDI, this disk is useless to most of us. Still, a few phone calls to Voce and Syco later, and the promise of Atari software (which should be available by the time that you read this) was extracted. The fully-featured patch librarian contains a library of the factory presets, and the editor has an edit buffer, a MIDI "global" page, plus a waveform editor with "virtual drawbars". A what with a what? Remember patch numbers 56-63? Well, these are the user-definable waveforms, which can be modified slowly and clumsily from the front panel of the DMI, or clearly, simply, and effectively using the editor. Drawbars are drawn on the screen, and these can be extended or pushed in using the mouse. Fourier analysis then converts the drawbar settings to waveforms, and these can be stored on disk and/or dumped to the DMI for inclusion in patches. This is additive synthesis, similar to (if more limited than) the system implemented on the Kawai K5, and almost identical to using algorithm 32 on a DX1 or DX5.

"Despite digital oscillators the tones are warm, if a little clinical, with a touch of movement even when all the effects are set to zero."

Editor/librarians usually cost serious money, but in 1990 Evolution Synthesis broke the mould by including an Atari editor free with the EVS1 module. Full marks go to Voce for following the same course. It's painful spending £500 on a budget expander only to find out that you've got to shell out another £100 to make it usable. Currently, Syco understand that the PC and Atari versions of the DMI Editor will remain free of charge, although you may have to dig deep for the Mac version expected later this year. I guess you can't have everything.

Extending the ideas behind the user-defined waveforms and the editor, I found that SysEx caters for patch and waveform dumps, and sample dump request will grab a waveform from any suitable external device. As an added bonus, the DMI will grab any 256-word MIDI SDS (sample dump standard) sample if a few simple conditions are met. Samples can be from 8- to 24-bits long, and can be looped forwards, backwards, or alternating. OK, so 256 words aren't very many, but if you've got an SDS sampler it must be worth editing a few waveforms and loading them into the DMI. This should enable you to create sounds that are not available via the DMI's own waveform generation.


A REAL ORGAN, whether it's got pipes or tonewheels, is the sum of two major elements. The first is the basic sound which, unlike most synthesisers, is a combination of many simple waveforms and pitches built up into more complex sounds. The resulting voicing can range from delightful delicacy to gut-wrenching power. The second element is the chorus, vibrato, phase and timbral modulation which modifies the basic sound.

So now for the good news: the Voce generates high-quality imitative waveforms and combines them in authentic ways into convincing organ voices. Now the bad: the Voce caters for a wide range of organ effects but each is, in isolation, disappointing. Unfortunately, DMI effects (with the exception of the distortion) can only be accessed one at time, so there is no facility to make the basic sound more interesting by combining them. Matters would be dramatically improved by providing another two LFOs, thus enabling each effect to be operated separately. Using simultaneous external effects creates a lovely warm and swirling sound - which sounds, funnily enough, not unlike a genuine organ. Replace the onboard Leslie effect with the wonderful Dynacord CLS222, the chorus and vibrato with a Quadraverb, and the distortion with a Roland GS6, and the DMI sounds excellent. Still, there never was a sound that couldn't be improved by over £1200 worth of effects units, so it's not really a fair comparison.

On the positive side, the range of facilities offered by the DMI and its attendant software make this a unique synthesiser with many well thought-out facilities. There are drawbacks - notably the operating system and the lack of real-time controls - but much of this can be forgiven. The MIDI musician has, if you'll excuse the language, never had a decent organ at his (her?) disposal, and has had to sacrifice valuable synthesiser polyphony to obtain even a rough imitation of the real thing. The Voce changes all that. So it doesn't sound like a B3 (or even a BX3) screaming through Deep Purple's PA, but it doesn't sound like a Bontempi either. On balance, for less than £500, and with the long-anticipated Roland VK1000 weighing in at a bank-breaking £1800, the Voce has to be the successor to the much loved, but now defunct Korg CX3. On this basis, it comes cautiously recommended.

Price £445 plus VAT.

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


Music Technology - Sep 1991

Gear in this article:

Sound Module > Voce > DMI64 MKII

Review by Gordon Reid

Previous article in this issue:

> Peavey 308S Monitors

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> Question Time

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