Synthesist Ian Boddy weighs up the pros and cons of incorporating MIDI expanders into your present set-up and briefly assesses one particular model - Roland's Planet-S.

Who can remember those halcyon days of the early Seventies when keyboard players were allowed to indulge in their favourite onstage pastime of mountaineering? Yes, surrounded by walls of gear they could flap about like demented windmills striking up all sorts of poses with legs akimbo and arms sticking out at every conceivable angle. Every now and then they would hurl themselves towards the summit of their keyboard stack and with a bit of luck reach that top chord while hanging on grimly with whatever appendage happened to be free at the time. Of course, our synth friends had their excuses for all this excess; they couldn't strut about like guitarists so they had to catch the audience's attention some other way.

Jesting apart, a rather more justifiable alibi for carting about all this gear was the synthesist's perennial dilemma of interfacing problems. Each manufacturer used their own system so that chaos reigned and if you wanted several keyboards of various makes then you had no option but to take them all with you on the road/in the studio and to play them individually. Until (yes, you've guessed it) MIDI came along and solved all of these problems overnight (well almost!). This supposedly universal interface system, after a few early hiccups, is now beginning to settle down and become rather useful, allowing just about every bit of gear (be it a synth, drum machine or Bedford van) to talk to one another far more efficiently than the old CV/gate set-ups ever allowed.

Apart from all the various sequencing tricks that MIDI can come up with, its main advantage is in allowing one keyboard to control several others simultaneously. Furthermore, recent developments have seen the arrival of MIDI modules on the marketplace that contain the synthesizing power of the familiar models they are derived from while existing within small (usually black) boxes totally devoid of any keyboard. Their advantages are manifold: they are more compact than full synths and hence easier to transport, which in turn makes them cheaper (hurrah!) and therefore more affordable to more people. They are also very easy to setup as well as sounding just as good as any full keyboard instrument. And the disadvantages? Well, of course, with this new-found interface ability and portability, there's no longer any excuse for getting up to all the mischief described at the beginning of the article. In any case, there are plenty of keyboard controllers available that can be slung around your neck whenever you feel like joining the guitarists in the band and strutting your funky stuff at the front of the stage.

Not content with producing sound modules without a keyboard, some manufacturers have come up with keyboards without any sound! What next, a box that doesn't do anything? Well such systems, for example, the Roland Mother keyboard or the Yamaha KX88, aren't as pointless as they may at first seem. Such instruments possess MIDI and so can control a series of MIDI sound modules allowing the performer to obtain complex layers of sounds with several split points etc, all of which can be programmed into various memory and patch locations onboard the master (mother) keyboard. Thus from one instrument a musician can produce on-stage incredibly complex sound textures that in the past could only have been created in a multitrack studio. In fact, the MIDI modules in such a set-up could be mounted in a rack and be located off-stage - certainly a more efficient and tidier system than that described earlier on. The actual physical construction of such mother keyboards is also of a higher standard than your average synth, providing the musician with quality weighted keys for a more expressive performance than is catered for presently by plastic keyboards.

At this juncture, let us take a look at a reasonably-priced MIDI module to see what functions one can expect from such a unit.

PLANET-S

The Planet-S (or MKS-30 if you prefer), is a member of Roland's Mother Keyboard MIDI family and for those of you unfamiliar with this particular module, let me tell you that it is essentially a touch-sensitive JX-3P in a black box. It is rather more sturdy than Yamaha's equivalent unit, the TX-7, and it has one immediate advantage for studio use in that it is possible to mount it in a 19-inch rack which should help keep things all nice and tidy on stage likewise.

Listing its voice capabilities I see as unnecessary since most of you should be familiar with a JX-3P, but in case you aren't, a brief resume of its sonic potential should suffice to jog the old memory banks into action.

The MKS-30 incorporates a fairly standard dual DCO (digitally controlled oscillator), six-voice polyphonic synth with all the faithfuls such as low and high-pass filters, envelope generator, low frequency and envelope modulation of DCOs and filters, stereo chorus, DCO sync etc. Get the picture?

All the controls are on the front panel and all MIDI and signal sockets on the back. It's onboard memory capacity is 64 programs with another 64 being present on either the provided ROM or the optional RAM (M-16C) cartridges. Thus at any one time 128 sounds are available which certainly beats the TX-7 out of sight, although no cassette storage facilities are provided (unlike the TX-7). The volume control, in the case of the Planet-S, is a humble slider on the far left next door to a brilliance slider which acts as an overall brightness control (raising or lowering the cutoff frequency of the filter by one octave).

Whilst the MIDI facilities of this Roland unit are adequate they are by no means as sophisticated as those of a device like the Yamaha TX-7. In common with the TX, it can receive on any MIDI channel but the main info it accepts is program change, pitch, key velocity, hold-pedal, pitch-bend and modulation.

Unfortunately, after-touch is not present on this unit although the larger Super-Jupiter (MKS-80) module in the range - which is similar to a JX-8P - does provide for this.

As per most modern synths, especially Roland and Korg models, the memories are divided into banks of 8 programs, which at times can make program location a bit fiddly, but don't worry if your master keyboard doesn't use this system. For example, when the Planet-S is MIDI'd to a DX7, the internal 32 voices on the DX on combined program change take the Planet-S from Bank 1/Memory 1 up to Bank 4/Memory 8. On switching the DX7 to cartridge, the 32 DX memories then take the Planet-S up from Bank 5/Memory 1 to Bank8/Memory 8. However, if your ROM or RAM cartridge on the DX has two banks, switching from Bank A to Bank B will not allow you to directly access the Planet-S cartridge memories; these have to be switched into play manually by means of a pushbutton.

PROGRAM EDITING

Next, let us take a look at the editing of the voices on this unit which was the great bone of contention on the TX-7 when it was first released. Fortunately, it is possible to modify sounds directly from the front panel of the Planet-S although by no stretch of the imagination is it an easy task.

To commence, you must first press the front panel Parameter button to access the edit mode and then select a two-digit number which represents a certain sound function. The double display window will then show the selected parameter number on the left and its current value on the right. Incremental up or down buttons are then used to change the particular parameter selected. When editing is complete, pressing the Parameter button again returns you to the play mode whereupon the display reverts to its normal function readout showing bank number on the left (prefixed by 'C' for cartridge voices) and program number on the right. Well, as you can comprehend, this is a tediously fiddly procedure calling for much referring to the owner's manual to identify which function is represented by what number. This totally numeric approach is slow and cumbersome but is certainly better than nothing at all. The Roland PG-200 programming unit originally designed for the JX-3P saves the day however, in providing nice tactile controls such as knobs and switches to change the sounds. The bonus of this unit is that with it, editing of sound parameters can be undertaken in the play mode without recourse to using the parameter/value method outlined previously. Unfortunately, this is going to add quite significantly to the cost but it is certainly well worth it in allowing editing to be carried out easily, quickly and efficiently. Finally, let me point out that it is very easy on the Planet-S to rearrange programs throughout the memory using a copy facility and to freely interchange programs between cartridge memories.

SUMMARY

The Planet-S is undoubtedly a nicely designed unit - nothing spectacular but still capable of producing quite a wide range of good, full-bodied analogue sounds. Obviously the inclusion of touch-sensitivity makes all the difference to the basic JX-3P design and the allowance made for editing facilities - either onboard or via the extra PG-200 programming unit - means that the Planet-S can easily be used by any MIDI keyboard owner as an expander module in their system. The only real drawback seems to be the price. It is typically selling for around £750-£800 and viewed alongside other expanders on the market like Korg's EX800 or Chase's Bit Expander, you start to wonder about little things like value for money...

In essence then, a MIDI expander gives all the source power of the synth it is derived from in a more cost-effective form. This allows you to add to your system to gain the maximum synthesizing power for the minimum cost. In general, it would seem wise not to put all your sound-eggs in one basket as different forms of synthesis give totally different characteristics to your sound. If you already own an FM synth it would seem a good move to widen your scope of available sounds by buying an analogue-type MIDI module such as the Planet-S, or vice-versa.

MIDI modules are definitely here to stay and you'll undoubtedly see more of them creeping onto stages and into studios in the future, but they do have some disadvantages despite the fact that they would seem on the surface to be the best thing since sliced bread. Inevitably compromises have to be made in squeezing a full-function synth into a small, black box and, as we have seen above in the case of the TX-7 and Planet-S, this is more often than not manifested in limited program-editing facilities. Nevertheless, as MIDI becomes more and more ubiquitous the spread of such MIDI expanders will continue and the keyboards to control them will equally become more sophisticated.

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