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Gem S2 Music Processor

GEM's newest synth, with its polished sound and presentation, could be set to dispel the company's homely image. Martin Russ discovers the multi-faceted GEM S2.

Can you name three Japanese hi-tech keyboard manufacturers? No problem. Three American? How about European? I will give points for Cheetah, Waldorf, EMS, Serge, Kobol, and Novation, but who else is there? If I mentioned Elka or GEM then you might think of organs and pianos, but behind both of these names is the Italian company Generalmusic (sic). Serious synthesizer enthusiasts may have heard of Generalmusic's work on large, state-of-the-art (and very expensive) sound synthesis research. The GEM S2 (and the S3 variant with its 76-note keyboard), however, is a new pro musical workstation — the combination of a powerful synthesis engine, master keyboard functions, and a sequencer into one integrated package. In a world already full of workstations, the S2 needs to have something really special to distinguish it from the rest — and it looks like it may have just that...


Generalmusic call the S2 a Music Processor, which makes it sound more like an effects unit than a serious tool for creating music. At first glance, it looks much like other high specification sample + synthesis (S+S) workstations, but there are several innovative features which set it apart from the crowd, and show that just looking at specifications can be misleading. In fact, given that the S2 extends the basic workstation idea by placing much more emphasis on live performance, 'Music Processor' looks like an apt description for this mix of workstation and performance synthesizer.

Although this is a review of a full production model of the S2, the basic design of this instrument means that it is inherently flexible. You can add software 'options' which extend the S2's capabilities, so the machine you buy can evolve to suit your own requirements. Future software updates may well offer additional facilities way beyond those described here, and Generalmusic have already demonstrated some very advanced prototype 'options' which show that the S2 can become considerably more powerful than the 'basic' machine reviewed here. Four or five options are due for release in September.

Peavey's DPM3 takes a similar flexible approach, but stores its software in ROM, which means that changes to the way it produces sound involve hardware modifications. In contrast, the S2 allows extra software to be loaded into RAM from floppy disk — rather like the Casio FZ1.


Many workstations seem to be little more than a synthesizer, a sequencer, a drum machine and an effects unit, all squashed into the same box. The result often provides little improvement over the separate parts, and is made all the more complex by the different sections' divergent and often inconsistent control software. The S2 is very different. The boundaries between sound synthesis, sequencer, multi-timbral setups, and performance aspects of this instrument have all been blended together into a surprisingly coherent whole. It really is quite stunning to be faced with an instrument where layering to produce a stack is the same as setting up a multi for use with the sequencer, and where an effect or a sound can be stored in a huge on-board library, to be recalled later without the need for an external computer librarian.

Added to this is the S2's 'multitasking' ability. At its most basic, this means that you can load a new song whilst the previous one is playing, or play the keyboard whilst the disk drive is active, but the S2 takes things further. You can start to edit a sound, go back to your previous performance setup and play around with layering, play the loaded song, edit some performance controls, and then go back to the editing of the sound, and find your edit screen just as you left it, with the cursor in the same place. Coming across things you were trying out some time ago and finding them just as you left them is disconcerting the first time it happens, useful the second, and marvellous the third. Blinking LEDs to indicate 'pending' tasks make the S2 one of the first instruments I have seen which allow you to potter about as you like without needing to stop and save everything every time you move from one function to another. In fact, this 'go back to it later' approach is so similar to the way in which people work that I would say that the S2 is a preview of the future — all instruments should be like this.


The LCD is the focus of much of the user interface, with lots of selector buttons clustered around it. The left hand side concentrates on the sequencer tracks, whilst the right hand side has a page-based system using dedicated page buttons and softkeys. There are more than 90 switches, so there is very little need for multi-function labelling, but the grouping of functions means that you aren't overwhelmed by the impression of too many buttons. Many of the buttons select a specific 'mode'; attention then moves to the LCD and the softkeys, with a second press of the button returning to the original state.

The S2 provides instant access to 100 stored Performances. A Performance is almost a complete configuration of the instrument, including such information as the routing of data between the keyboard, the sequencer, and the sound generators. Performances are stored in Banks of 10, and each Bank can also be associated with a Song. A Setup is a snapshot of the entire instrument, including the user samples in RAM, the songs in memory, the sounds and effects, and all the Performances. Much of the complexity normally found in workstations is absent here — the S2 works with exactly the right groups of data whilst still retaining the ability to save and load single sounds or MIDI Files if required. Because none of the user RAM, for samples, sounds, and sequence data, is battery backed (more on this below), the Setup is a valuable memory management tool.

Sequencers and multi setups are normally one of the most complex parts of a workstation, but the S2 simplifies things with the concept of 'Tracks' — users of Ensoniq keyboards may find some familiar concepts here. There are 16 Tracks, each of which can be assigned to (ie. controlled by) the S2's keyboard, the sequencer, or a channel from one of the two MIDI In sockets. On the output side, the Track can be connected to the MIDI Out sockets, the internal sound generation, or both.

The Track selector buttons are used to mute tracks or select them for the S2 keyboard to play, with just one or two presses — there is no need to worry about which MIDI channel the keyboard is on, since the Tracks only refer to channels at the MIDI Input or Output.

On many workstations, effects are a problem, because they are often included as part of the single sounds for editing purposes, whilst for multi-timbral use only one effect setting can be used at any one time. The S2 makes things conceptually easier, because effects are part of a Performance. If a Performance uses just one sound, then that sound has its own dedicated effect. If it's a multi-timbral Performance, then you have the same effects capability, and route sounds to the effects on a Track by Track basis.


The S2's synthesis draws on a combination of fixed ROM samples and user samples in RAM, providing versatile and wide-ranging sound possibilities, whilst the individually assignable sample-to-note mapping allows easy drum control. Samples are a mix of single cycles, complete instrument 'recordings' and series of shorter samples. There are two major modes of sample playback: dual and crossfade. In dual mode, both oscillators use the same sample, but you can alter the detuning between them, which opens the way for excellent 'analogue synth' sounds, whilst in crossfade mode, you can velocity switch between two different samples.

Sounds can apparently be programmed with just one oscillator instead of two, which doubles polyphony to 32 notes, but no examples are provided in the sounds on the current version of the S2, and it is not possible to change to one-oscillator mode from the S2's present controls. In fact, there is no way to 'initialise' a sound; you merely edit an existing voice and then store the edited sound in the library. This seems to be the one weak area of the S2's synthesis section — some parameters seem to be factory-alterable only, and this is particularly noticeable for the sample playback. You choose a sample, and that's it; no provision for looping (forward, reverse, or alternate) of samples, and no dual mode without crossfading unless you use layering. The review S2 could only load user samples from disk, but a software option to enable MIDI sample dump reception should soon be available.

The two independent filters have a remarkably smooth 'analogue' sound, with resonance all the way into self-oscillation. They can be configured for low pass, high pass, band pass, or 'Presence Cut/Boost' operation, all of which add up to some very effective timbral variations. Not since the legendary Yamaha CS80 have I experienced the wonderful resonant band-pass filter sweeps that the S2 can make. The pan section is part of the S2's synthesis, and has its own envelope and random position capabilities.

The effects section is in two parts: Effect 1 can produce Static Effects (GEM-speak for reverb and early reflections), and Effect 2 handles Dynamic Effects like delay, chorus, phasing and flanging. Because of the separation of the effects section from the synthesis section, it is not possible to control the effects with any of the synthesizer controllers, which is a pity, but the simplicity of the Track system would probably be compromised by any attempt to route synthesizer controls to the effects.


Just when I thought that there was no room for innovation in the design of the boxes to put around keyboards, along comes the S2. When I first unpacked it, I was struck by the unusual 'feel' of the casing — it feels soft and perhaps even rubbery. On closer examination, it turns out that the strong metal extrusion and structural plastic casing has been coated in a matt plastic finish — and I mean a solid, deep matt black. To the hands it feels silky smooth and, dare I say it, almost erotically sensual, whilst to the eyes it reflects almost no light at all. It ought to be near perfect for on-stage use, where the last thing you need is reflections of coloured lights getting in your eyes all the time. In complete contrast, the covering for the LCD is very reflective — although the backlit LCD is one of the clearest and brightest I have seen on any equipment. The front panel control for LCD viewing angle is a welcome inclusion.

The layout of the S2 follows all the usual trends. The high density disk drive is on the left, just above the two assignable wheels, which are made of rubber, and look like two flattened eggs poking up out of the surface. With my keyboard-testing, sweaty, greasy hands, I had some problems in getting a good grip on the slightly textured rubber surface — I would have preferred more texture. I felt that the centre detenting on the modulation wheel was a little light but then it is designed to cope with unipolar and bipolar parameters, whilst the pitch bend wheel exhibited an under-damped oscillation as it settled after it was pulled to an extreme setting and then released.

The keyboard is a bouncy, slightly weighted, plastic design, and scores extra points for supporting polyphonic aftertouch; you can adjust the aftertouch response with a small control beneath the keyboard. Whilst the casing is matt, the keyboard is sharp and shiny — I say 'sharp' because my thumb became sore as it rubbed against the burrs left along the sides of the keys. As with any keyboard instrument, you need to check out how the keyboard suits your own playing style — when I asked the S2 Product Specialist at the UK distributors Bluebridge, he had not noticed any thumb problems, so it could just be my playing style.

The upper surface is dominated by the LCD. Seven track selector and control buttons are on the left hand side, whilst the seven buttons on the right are softkeys whose function is determined by the current page. Two pairs of buttons on the upper left and right act as page up/down controls, with occasional use as 'Save' buttons. The left hand side of the surface has eight sliders — one master volume and seven assignable controls with assignable buttons underneath them. The way these sliders work speaks volumes about the effort which has been put into the design of the S2 — you can use them as 'quick edit' controls to make tweaks to the volume balance, attack, release, filtering or panning of the sounds, but not quite in the way you might expect. Instead of having seven sliders for seven parameters, you select a parameter to control, and then the sliders will control that parameter for the seven tracks or multi-timbral parts which are displayed in the LCD window. This allows the rapid setting up of balance, brightness or phrasing for the different parts in context, in realtime and intuitively.

Alternatively, you can assign the sliders to MIDI Controller Numbers — particularly important in an instrument which has a strong GM bias since many of the performance controls are mapped to MIDI Controllers. The buttons which normally select the 'quick edit' parameter can be re-used in this mode as general-purpose MIDI Controller buttons, opening up more control possibilities.

Immediately to the left of the display are the editing buttons and the source selectors. Editing is based around four buttons covering Performance, Track/Multi setup, Sound and Song — with a fifth button for additional 'option' software. The Source buttons enable control of MIDI sources: Local (the S2 keyboard and performance controls), MIDI In, and the Sequencer. In conjunction with the Track setup editing button, these allow you to control the configuration of the Local keyboard and controls, incoming MIDI and Sequencer, and how they interact with Sound generation and the MIDI Outputs. You can save this configuration as a Performance, so it is possible to switch from an S2 which looks like an expander to an S2 which behaves like a master keyboard, just by selecting a new Performance.

This avoids all the complexities of which channel the local keyboard is on, whether Local Control should be On or Off, and how you use an external sequencer. The graphical display showing the Local Keyboard, MIDI In, Sound Generator and MIDI Out, with Track controls in between, must be the most transparent of any MIDI configuration I have seen on any synthesizer. Full marks to Generalmusic, and another example to other manufacturers of how it should be done.

On the right hand side of the display are the data entry dial, and Enter and Exit buttons, as well as the increment/decrement buttons and the numeric keypad. The far right holds the Performance and Bank/Song buttons. Just in front of the LCD are the sequencer transport buttons, and along the front edge of the panel are the Preload button, for loading new songs into memory in the background, and the Sound and Effects Library buttons, allowing access to the on-board library areas, where you can audition, edit, move, save and load to/from disk, and search for names — all the functions for which you would normally need an external computer librarian. At the risk of repeating myself, on-board libraries like this are another S2 innovation that ought to be on all workstations.

Inside the S2, build quality is high — a few neat ribbon cables connect the six main PCBs together. A surface-mounted Motorola MC68302 microprocessor dominates the main plated-through hole, solder resist and silk screen legended PCB, as do the four VLSI custom ASICs for Signal Generation, Filtering and Effects processing. Three 2MB ROMs hold the samples, and the operating system is in two EPROMs (dated 15th June 1992 on the review model — only a couple of weeks before the keyboard reached me). There are four Analog Devices ADI 865 stereo 18-bit DACs, which should produce eight audio outputs instead of the six found on the rear panel.

The DACs have their own power supply regulators — presumably to avoid noise problems from the switching mode power supply. The analogue output filters use standard TL074 and LM324 op-amps rather than the NE5534 low-noise op-amps found in some other designs. The polyphonic aftertouch is achieved by individual conductive rubber sensors beneath each key, and keyboard scanning is carried out by a Z8-derived processor. The RAM chips are soldered-in SIL packages, and not the socketed SIMMs found in many sample based instruments. The MIDI sockets are filtered to avoid EMI and RF interference problems. Most of the miscellaneous TTL logic used is Motorola or Toshiba PIC or AC 74 series.


The sequencer has 16 tracks, plus a master track, and is designed for real-time recording with subsequent 'microscope' event list editing. The resolution is 1/192nd of a quarter note, which is fine for all but the most exacting of uses. With up to 2MB of RAM available (the RAM is shared between the sequencer and edited sounds — sample storage gets a separate 2MB), you can record around 250,000 events into (up to) 10 songs. Editing functions include erasing, deleting and moving events, scaling dynamics (velocity), transposing, quantising, copying and appending bars. The master track can be used to set events which are common to all tracks: Tempo changes, Volume, Effects parameters, etc. A 'juke-box' function allows the songs in memory to be played in numerical order one after the other.


Unlike many instruments where General MIDI (GM) compatibility seems to have been added on late in the development cycle, the S2 seems to have been designed for GM from the beginning. The numbering scheme used for the 350 ROM sounds matches the GM Level 1 specification of Program Numbers to sounds, except for the S2's Drum Kits, which occupy Program Numbers 121 to 128 (the Sound Effects Group). The S2 extends the basic 128 sounds by using the MIDI Bank Change message (Controller Number 0) in much the same way as Roland's GS Standard. Bank 1 holds the GM Level 1 'Base' tones, and there are a further 15 banks for 'variations' of each sound.

With the GM spec defining rather boring and conventional basic sounds, some of the best synthetic sounds in the S2 are the variations: 81-1 is defined as Lead 1 (square), and has 11 variations, whilst 82-1 Lead 2 (sawtooth) has 13 variations. The S2 certainly does have a strong capability in the 'sophisticated analogue synth' area, and many of the sounds recall the legendary Elka Synthex.

You can save your own sounds to any unused locations, which means that there is storage for (128 x 16) 2,048 sounds, although 350 of these are already used up by the ROM presets. You are unlikely to use all the remaining 1,698 — either the 2MB of sound/sequencer RAM or your patience will run out. The RAM in the S2 is not battery-backed, so you need to save your work to disk regularly; in this respect, working with the S2 is rather like working with a computer. Note also that the RAM is not in the form of SIMMs, which makes increasing the S2's on-board user sample RAM difficult. I would have expected SIMMs (or expandable RAM) and battery backup, given the competition from instruments like the Yamaha SY99 or the Peavey DPM3. The S2 has no provision for memory card storage and no way to access a CD-ROM or hard disk via SCSI — the disk drive or MIDI bulk dumps are your only options for saving data. With no battery backup, power failure whilst on stage could be disastrous — which is probably why the S2 will automatically reload itself from a disk on power-up. (Make sure you save the current setup to disk!)

With a pair of sockets for each of the MIDI In, Out and Thru ports, the S2 can cope with 32 independent MIDI channels. In combination with the sophisticated and versatile Track configuration, this makes the S2 a very powerful master keyboard for use at the centre of a MIDI system.


Whilst the S2's emulations of real sounds are good enough, the instrument's true strength is in analogue/digital composites. The comprehensive filtering options allow the programmer to indulge in some serious squeezing of timbres, whilst the ease of setting up and controlling layers and tracks make it a fast, powerful player's instrument. The ability to edit 'live', and the multi-tasking, make this a great instrument to work with in almost any situation.

I was impressed. I started out expecting just another S+S workstation, but found a musical instrument which ignores many of the conventions and whose designers were confident enough to do things their own way. They have succeeded — the S2 may work differently to other instruments but, once learned, it is a vast improvement over the other workstations I have used. My only reservations concern the lack of RAM expandability via SIMMs, no SCSI/SMDI port, and the 'depth' of some programming parameters. If the Peavey DPM3 is any guide, then the software updates should easily rectify most of my programming concerns.

The S2 is definitely worth a serious look, listen and play for anyone who wants a workstation which will also pay its way on stage. You could try hiding the GEM logo and ask a few friends who they think made this keyboard — they'll be surprised. This is no 'home organ' derivative but a thoroughly professional instrument which deserves to be up at the top with the best — and it's European!

Further information

GEM S2 £1,995; S3 £2,250. Prices inc VAT.

Bluebridge Music Ltd, (Contact Details)


  • PCM sample-based S+S synthesis, with subtractive synthesis post-processing
  • 3 MWords of sample ROM; 1 MWord of user sample RAM
  • 32-note polyphony (but typically 16-note with paired oscillators)
  • 16-part multitimbral
  • Reverb and Modulation type effects sections
  • 100 Performances
  • 10 Songs
  • 350 ROM preset sounds
  • GM/GS Standard Program Change mapping
  • 240 x 64 pixel backlit LCD display
  • 3.5" HD floppy disk drive (reads ST and PC disks)
  • 16-track sequencer
  • 192ppqn sequencer resolution
  • 250,000-event sequencer capacity
  • 2 MIDI Ins, with merging
  • 2 MIDI Outs (32 channels)
  • 2 MIDI Thru sockets
  • Stereo audio output
  • 4 assignable independent outputs

Also featuring gear in this article

Previous Article in this issue

Wayne's World

Next article in this issue

Drum Programming

Sound On Sound - Copyright: SOS Publications Ltd.
The contents of this magazine are re-published here with the kind permission of SOS Publications Ltd.


Sound On Sound - Aug 1992

Review by Martin Russ

Previous article in this issue:

> Wayne's World

Next article in this issue:

> Drum Programming

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