The Opera 6 gets improved MIDI facilities, a cosmetic spring-clean and a significant reduction in price. How does it rate now?

As far as the basic specification is concerned, the new DK600 is almost identical to its predecessor, the innovative Siel Opera 6. That is to say, a programmable six-voice MIDI polysynth with two oscillators per voice, a VCF and a VCA, and a touch-sensitive keyboard which, seeing as the Opera was released marginally earlier than Yamaha's much-lauded DX7, made it a first for an instrument in this price category (under £1500).

The Italians pride themselves in their design skills, and while the Opera 6 was no eyesore, its successor is a definite aesthetic improvement. The layout of the controls is similar, but each control section is now distinguished by a pale blue outline instead of the solid blue background of the previous model, which tended to distract players from the job in hand.

However, the most significant changes are ergonomic as well as aesthetic. You may recall that the Opera 6's facia design incorporated small white pushbuttons (only 18mm apart) for program change functions. These were fiddly and unpredictable in live situations, and have therefore been replaced on the DK600 by a single row of (much larger) switches. Unfortunately, changing patches still requires three button pushes (two digits followed by Enter), and although this system enables you to select a new patch in advance of when you actually need to use it, the process is just a little too time-consuming to be a complete success.

Oscillators

The major hardware improvement incorporated into the DK600 lies in the fact that its oscillators are now digitally - as opposed to voltage - controlled. The good news is that these improve tuning stability and fine-tuning facilities, but the bad news is that no additional control options over and above those on the Opera 6 have been made available.

To be fair, the Opera's controlling possibilities are pretty good anyway. Oscillator A is taken as the reference pitch, while B may be coarse-tuned almost a fifth down from it: the fine-tuning control makes a difference of almost a semitone in each direction, and using both controls together, at maximum 'flatness', puts the oscillators exactly a fifth apart.

There is no provision for reducing the output of Oscillator A, but there is a Half Volume switch for B, while a level control for Oscillator A's noise element allows some sound-blending to be carried out. Both sound sources can produce pulse or ramp waves (or both together, or none at all), and both incorporate 16', 8', and 4' octave range options.

Somewhat confusingly, the DK600's front panel credits it with three LFOs, but in fact these are governed by only two sets of controls. Notionally, LFO1 controls the pitch modulation of Oscillator A while LFO2 controls that of B, but as these share the same set of Depth and Speed controls, the presentation is a little misleading. LFO1 is entirely separate, and may be directed to control either Pulse Width Modulation and/or the operation of the DK's filter.

Again, the DK600's filtering section is identical to that of the Opera 6 (ie. a 24dB-per-octave low-pass design), which is probably no bad thing, since filtering was one of the things the previous Siel did rather well. There are six filters in all - one for each voice - and these are all programmed by a simple set of controls, viz Cutoff Frequency, Resonance, and ADSR Amount, with a switch for keyboard tracking.

"The DK600's filtering section is identical to that of the Opera 6, which is probably no bad thing, since filtering was one of the things the previous Siel did rather well."

Unusually, the Siel also incorporates a Dynamic ADSR section that can be assigned to either the VCF or the VCA, while the keyboard touch-sensitivity (programmable for the first time on the DK) may be directed to control this ADSR level or the attack time (or both, or neither). If you're a competent player, or even someone experiencing the joys of touch-sensitivity for the first time, these features should prove invaluable.

MIDI Functions

The DK600 is the first Siel synth to incorporate a fully-developed range of MIDI software facilities. As a result, it can receive information sent to it in either Omni or Poly modes, and can interact fully with Siel's own MIDI Expander and MIDI-equipped instruments from other manufacturers.

Selecting a Poly mode Channel number is accomplished by accessing voice preset 96 (which is, obviously, blank), and entering a number from 1 to 16 - or as the Siel system would have it, 00 to 15.

A further refinement lies in the facility for using MIDI to receive keyboard-split information. The way it works is this. The DK600 uses MIDI data to re-define the synth's keyboard so that it controls the DK's internals at the upper end and those of the connected MIDI instrument at the lower one. The precise point at which this split occurs can be set anywhere simply by pressing the appropriate key, and on each of these occasions, the Enter button works as a Return function, and the change is written into the DK600's software.

Conclusions

Sonically, the DK600 is little different from the Opera 6. In other words, it possesses a distinctly European character that makes it pretty good at brass imitations, OK for strings, and as good as any other instrument in its class at producing 'synth' noises of various descriptions. Digital control has given the DK a strength at reproducing percussion sounds too: the factory bell/gong preset - among several voices that make use of the instrument's programmable dynamics - is particularly impressive.

Not surprisingly, the DK's strengths and weaknesses are similar to those of its predecessor, but the most dramatic change - the £300 reduction in asking price - has made it an altogether more attractive proposition. Just think, the DK's programmable dynamics and split-keyboard facilities almost match those of Roland's mother keyboards, but it does it all at a fraction of the price.

I freely admit that the Siel's characteristic sound is not my favourite, but even if it isn't yours either, the DK's performance functions make it a mighty impressive package, all things considered.

RRP of the DK600 is £999 including VAT. Further information from Siel UK, (Contact Details).