The trouble with investing money and time in a modern synthesiser is that you know it'll soon be out of date. You can only hope that someone designs an upgrade for it - like the MEX board for the D50.

ALTHOUGH THE ADVENT of the modern breed of hybrid sample reader/synthesiser instruments was heralded by Roland back in 1987, the D50 has, in just two years, been dramatically superseded by synths such as Korg's M1 and Ensoniq's VFX. Without entering into an argument about the relative merits of these instruments, the Korg and the Ensoniq certainly boast better MIDI and performance facilities than the D50. Since many D50s and D550s now spend their lives in MIDI rigs, it's time someone updated them. Roland haven't, so German manufacturer Musitronics have grabbed the opportunity to launch their MEX (MultiMode Expansion) board (for D50 and D550).

The MEX offers 64 extra onboard memories, two eight-channel multitimbral modes, the ability to create multi-voice sounds, and expanded master keyboard functions. The ads also mention six LFOs, two chorus units, two equalisers, and a reverb section, which is a trifle strange, because these are part of the basic spec of the D50. Perhaps what Executive Audio mean to say is that these facilities can be put to much better use with MEX - as we will see.

MISE EN SCENE

THE D50 REMAINS the most sophisticated synthesiser that Roland have yet produced. Its characteristic sound, which is created from a combination of PCM samples (generally of the attack portion of a sound) and sounds created within its conventional analogue-style synthesiser section, is still highly sought after. Two of these basic sounds, (Partials), form a group known as a Common Block and these may be chosen freely from the PCM and synth sections. A Common Block, plus a number of other parameters makes up a Tone or Voice, and two Voices constitute a Patch. There are 100 PCM samples in the D50, some of short duration (one-shot), and some loops. There are also PCMs formed of other samples, some looped, some not, and these are included to help create the more obscure special effects of the D50.

A patch can be layered on the keyboard in a number of ways. The most common structure is Dual Mode - all four partials play across the whole keyboard - giving the classic D50 sound, but restricting you to eight-note polyphony. Whole Mode allows 16 notes to be played but the synth is then restricted to one voice (two Partials) across its keyboard. A little more flexibility is offered by the various Split Modes, but in all of these you are still limited to four partials, split two by two and allocated either side of a keyboard split point. For use with sequencers there is a Separate mode, which enables the two Voices in a Patch to be played on different MIDI channels, and this gives a crude multitimbral capability - but limited to two eight-note polyphonic voices. Chorus and EQ can be separately defined for both voices, but there is only one onboard digital reverb which can be selected to act on just one voice, or the whole patch.

ENTER MEX

THE MEX COMES in a box containing the board and a 30-page manual. The manual is well presented although it suffers from occasional attacks of Germlish, and there's one major typo where the end of an explanation is missing. But these are minor quibbles. Work steadily from page to page and you'll learn how to safely install and use the MEX.

You have to remove 20 screws which hold the base in place. If the Operating System ROM is inserted into a socket on the main D50 processor board, installation of the MEX is extremely simple. Remove the OS ROM, solder one wire from the MEX to the motherboard, and insert the expansion into the empty socket. With a regular D50 it's unlikely that you'll come to any grief but, if your synth is one of the 10% whose OS ROM is soldered to the main D50 board, get an authorised service centre to install the upgrade.

THE PLOT

THE MOST OBVIOUS benefit of the expansion is the extra memory space - 64 traditional D50 patches or 64 MEX multi-patches, or any permutation of the two. The immediate impression gained after installation is that the expanded D50, with 128 memories, is much more flexible and more satisfying to work with. The MEX also has a spare socket which will take a further S-RAM chip and give the synth 192 internal memories. Unfortunately, Executive Audio were unable to say when this will be available, or how much it will cost.

Using the Internal button in conjunction with patch bank buttons 1 and 2 switches between the memory banks which are now named 'I' and 'X'. You can also move freely between banks using MIDI commands, and these are clearly laid out in the manual. The addition of 'X' doesn't adversely affect the patch facilities of the D50 in any way, and 'Write's and 'Copy's between Tones and Partials are also unaffected. Memory cards can still be accessed using Card, and patches or complete banks may be moved between the currently selected internal bank and the card itself. Bulk dumps over MIDI seemed equally unaffected, and 'Load's and 'Save's act on the current internal bank - be careful which is selected before you do anything you might regret. I only found one bug within the MEX software. In certain menus Shift types a "9', yet still fulfils its usual function.

The biggest selling point of the MEX board will be the full multitimbral capabilities it gives the D50. In a roundabout sort of way, this has been available from Roland for some time because, shortly after the launch of the D50, they released their MT32, which in many respects is a multitimbral D50 expander. The MT32 is a 32-note polyphonic, 128 onboard preset memory, 64 programmable memory (although these are volatile and have to be reloaded each time the unit is switched on), velocity (but not aftertouch) sensitive, eight-channel multitimbral L/A module. Got that? The 128 timbres supplied are of comparable quality to D50 voices, and the MT32 is able to play 32 notes simultaneously, of which each note is a single D50-type Partial. Of course, you can also build up full D50-type voices consisting of four partials each, or even go beyond this and (eventually) create a single 32-partial monophonic patch. So the MEX not only has to offer comparable facilities but, because the MT32 can now be purchased for under £300, should challenge the power and flexibility of a D50/MT32 combination.

Unlike the MT32, the basic architecture of the D50 only allows a maximum of 16 notes to be output at any one time, even if the MEX is playing a full complement of eight voices. Since the D50 can only hold two Common Blocks in its working memory, the MEX has to poke sounds directly out of the main RAM memory when required to play three or more voices simultaneously. This has no consequences for the sound, but because the buffer is not being accessed, edits have to be Saved to RAM before updates to voices within a multitimbral patch can be heard.

A multitimbral patch is organised as follows. A Master Patch (which would otherwise be a basic D50 Patch) is defined as a multitimbral patch using the key-mode button. This consists of the Upper and Lower Master Common Blocks which contain the EQ, Chorus and Tuning data that will be required by voices within the patch. However, instead of creating or copying four partials into the Upper 1&2 and Lower 1&2 partial memories, you allocate Multi-Tones within the Multi-patch memory locations. Eight Tones may be defined within a patch, and these can be played on any MIDI channel. There are no limitations on how many or how few Tones can be accessed by a given MIDI channel other than the limit of polyphony of the instrument. Each Tone within a Multi-Patch has four parameters associated with it: MIDI channel, volume, pan (left or right), and tuning. The appropriate parameter windows are accessed by pressing Patch twice, and editing, scrolling between windows, and all other control functions follow the methods used on the unexpanded D50. When a Tone is used within a Multi-Patch its own EQ, chorus and LFO parameters become inactive and are controlled by the Common Block. Sorry, it has to be like this - otherwise there just aren't enough EQs, LFOs, and Choruses to go round. This, then, places limitations on which Tones can be combined to best effect - for example, you can't successfully mix a heavily chorused Hammond with a flute. But this is a common problem for all synths with onboard effects - you just have to think more carefully about your Multi-Patches than would be necessary if you had 24 LFOs, eight parametric EQs, and eight chorus/flangers...

THE SUB-PLOT

THERE ARE TWO Multitimbral modes - MULTI and MLT-D (Multi-Dual) which can be selected by incre-(decre-)menting the key mode button, just as you would to select Dual, Whole, or any of the other key modes. In Multi, all eight Tones are fed to the upper master common block. This means that only one set of EQ and Chorus, and three LFOs, are utilised for all eight Multi-Tones. However, all 16 notes can then be dynamically allocated by the software. In Multi-Dual four Tones are allocated to each of the upper and lower common blocks, and dynamic allocation is limited to eight notes, although there are two groups of eight to play with. In addition, both sets of EQ and chorus, plus six LFOs are now available.

Unfortunately, using a D50 Editor/Librarian isn't painless any more, because these have all been written for the basic D50 system, and can't cope with Multi-Patches and Multi key modes. SonicFlight's D50 Capture! translates the Multi and MLT-D modes to Whole and, understandably, loses all the information regarding Multi-Tones and their associated parameters. Dumping Multi-Patches will therefore require a Generic Editor with a D50 template modified to include the MEX. I suspect that most users will have to resign themselves to storing Multi-Patches in the synth itself, since RAM cards won't handle them either. Still, what else were you going to use those 64 extra memories for? The manual includes five appendices giving MIDI transmit and receive data, and a complete listing of the Patch, Common, and Partial data types. Perhaps this information will be used to create a D50/MEX template in the near future.

"One of the criticisms of the D50 was its inability to use further PCM samples, so the ten new PCM waveforms in MEX come as a pleasant surprise."

Another important benefit of the MEX is Unison Mode. This isn't mentioned in the literature, nor in the adverts, which is strange, because the lack of unison is one of the major shortcomings in the D50 spec. This is how it works. Two new facilities, Transmit Upper and Transmit Lower, defined by Split Point parameter, enable the D50 to perform like a controller keyboard with an eight-channel expander attached. True Unison can be created by saving a voice to four memory locations and detuning it by slightly differing amounts in each memory. The Multi-Patch can then be built from these four almost-identical voices. Because of the conflicting detunings, this is almost as good as having eight analogue oscillators, and it certainly reaches parts that no other digital synth can. The physics of the L/A generation system (as implemented in the basic D50) will never let the unexpanded synth be a window rattler. But with the MEX, keep the gains down. In fact, the eight voice/16 Partial unison mode puts us firmly into Kawai K4 territory.

Key Windows are another aspect of the MEX. These define the range in which a Tone will play and, if you've defined all eight Tones to play on a single MIDI channel routed internally, you can have eight distinct areas on the keyboard, each of which plays a different sound. Complex overlays and crossfades can be created using pairs, or even higher combinations of sounds, and since all the Tones are independently tuneable and volume-able there are almost unlimited combinations possible.

When MT first reviewed the D50 (May '87) one of the criticisms was the instrument's inability to take further PCM samples into its memory. So the ten new PCM waveforms in MEX come as a pleasant surprise. These have been created by combining some of the original 100 PCMs in new ways. The ten PCMs, named Loop 25-34, can be accessed as PCM numbers 101-110 and offer an assortment of strange combinations of instruments looped together - such as Clarinet and Plucked Guitar, and metallic percussion and piano. The most complex of these is Loop 34 (PCM No. 110) which has 17 separate one-shot PCMs combined into a complex rhythmic and melodic loop. (Interesting, but can you think of a use for it? Musitronics don't seem to be able to, because they haven't used it in any of the 64 patches they supply on the board.) Of more interest are the further 15 PCM waveform slots (111-125) which are enticingly named Extend. It would be nice to see 15 genuinely new PCM samples in these slots, which would be of far more use than 15 weird and wonderful loops.

The first thing that most musicians do when confronted with a new synth is to play all the presets, and make sagacious comments such as, "This'll blow your q***ing K1 away". In many ways the MEX changes the D50 into a new instrument, so many prospective purchasers will, if they can get their hands on an upgraded machine, do exactly the same thing.

This is where the fun starts: some of the 64 new patches are among the best D50 voices yet heard. Worthy of special mention are the Hammond patches - 'And J Lord is lost behind this Hammond' (15) and 'Smell the dust on the old B3 Hammond' (56) (the factory names, honest). Amongst the basses, 'Mr Big Boom Boom plays the jazz bass' (13) is particularly good and Jan Hammer freaks will enjoy the expressive 'Distorted Paul' with its harmonic overtones creeping in as the note sustains. Patch 55 is a meaty analogue polysynth - 'Who stabbed the Oberheim Mr Roland', and 'Prophet T8' (85) combines an atmospheric digi-logue pad with a chunky synth-bass speaker-rattler. For genuine early '80s syn-drums try 'Mr Simmons why did you do THIS to us hmmm' (74), and for atmospherics 'GlassWorld in Fear' (81) and, finally, the patch that deserves a mention for its name alone - 'Do you speak Alpha Centaurian we seek a bar' (88). Names apart, these really are worth having, especially since most of them are Whole mode voices - two partials per patch - so they can be used as Multi-tones within Multipatches. There are a number of factory-set Multipatches supplied - most notably 'The band that scared the death away' (71) which includes Simmons drums, ride cymbal, bass, lead, and various brasses and pads. You can construct a whole track from this patch alone, without running out of voices.

To make the best use of its multitimbrality the MEX offers four further output modes (giving eight in all) which are new output combinations of upper and lower voices, reverb input, and reverb output allocation. These are selected using Mode values 5-8, and add that extra bit of flexibility for users who can't rearrange their Tones because of EQ and Chorus considerations.

The final touch is a button which sends MIDI All Notes Off to all Iones in the D50: a panic button.

VERDICT

GIVEN THAT YOU want to drag your D50 kicking and screaming into the '90s, there are many reasons why you might want to buy an MEX. But £300 is a lot to pay for a small upgrade board that offers only 64 extra memories (DX7 expansions have as many as 320), multitimbrality, and one or two other bits and bobs. However, this is one of those times when the whole is definitely greater than the sum of the parts. The convenience of the MEX, the simplicity of operation, the lack of MIDI cables and signal leads aren't facilities that you can justify in wonga. Executive Audio (MEX's distributor) claim that they can't get enough, and I believe them. For the die-hard D50 user - and there are a lot about - there's much to recommend the MEX, and I can see a lot of people digging into their pockets.

In the period that's taken us from the S10 sampler to the S770, the D50 has stood still. We've seen the D5, D10, D110, D20, MT32, and a host of newer, computer-oriented, L/A modules from Roland, but the original (and arguably the best) L/A synth hasn't moved an inch. Are Roland going to let the D50 fade away, or do they already have the D50 version II tucked away? If they haven't, they've a lot to thank Musitronics for, since without further development the D50 would disappear underneath piles of VFXs, M1s, K4s, and SY77s.

As in the microcomputer industry, where the open architecture of the IBM PC enabled IBM to outsell every competitor (many of whom had developed superior machines), music manufacturers need to offer upgrades, if only to reassure the punter that his pride and joy isn't going to be made obsolete at the next trade show. If the original manufacturers are unwilling to shoulder the responsibility, they should be grateful to those who are.

If you own a D50 or D550, should you be thinking of buying an MEX? You probably should. Although you can pick up a second-hand MT32 or even a Kawai K1R for less, the addition of multitimbral modes, Unison, keyboard splits and 64 memories make the D50 into a new synth. And there are many players for whom the D50 is an essential part of their life. The rest of us have to decide between a VFX, a K4, and a D50/MEX. Tough, isn't it?

Price £299.95 including VAT.

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