Introduced in 1994, the Korg X5 synthesizer was basically an update on the tone production engine of the world-beatingly successful Korg M1. From the M1's launch in 1988, and essentially through to the end of the 20th century culminating in the late '90s N Series, Korg used their AI² Sample & Synthesis system in synths and modules.
Above: The original version of the Korg X5, with 32-note polyphony.
Unlike the M1, however, the X5 featured no onboard sequencing – it was purely a synth, and not a ‘workstation’. Whilst the X5 was hardly a major advancement in technology from Korg (the module version of this keyboard had already been on the market for a while in the shape of the 05R/W), it did benefit musicians in some important respects. Firstly, the sound-programming system was widely known, so a large number of digital synth players would not need to learn a new concept. And secondly, the R&D cost for this synthesis system had been more than recovered, so purchasers were not going to pay premiums on the retail price. Relatively speaking, the X5 was an inexpensive synth, and in its day, it did offer a lot for the money.
The X5’s raw waveforms comprised hundreds of selectable multisamples – everything from the predictable range of pianos and organs to exotic instruments and drum kit sounds. Up to two of these samples could be combined in a basic Program Mode preset, with a variety of synthesis parameters and effects allowing the player to warp the sounds to taste. The user could then combine up to eight of these basic presets into a much more powerful ‘Combi Mode’ preset. In Combi Mode, the X5 could build some phenomenally big sounds with a heck of a lot going on. Combi Mode also incorporated digital effects, but these overrode the effects programmed into the basic patches in Program Mode. Combi Mode additionally allowed the user to allocate different MIDI channels to each of the composite sounds. That, in a nutshell, was AI².
The huge drawback with all of this was that the original X5 was only 32-note polyphonic. If you were stacking two samples per Program, and eight Programs per Combi, then with each sample taking up a voice (2 x 8 = 16), your Combi would only be two-note polyphonic (32 / 16 = 2). The fewer samples you managed to use per preset, the greater the amount of polyphony you retained. Of course, it was quite possible to create good patches using just a single sample, and that would allow the full 32-note polyphony.
Above: A Korg X Series ad from late 1996, showing the standard Korg X5 reduced to a lower than previous price of £499, with the 64-note polyphonic update the Korg X5D priced at £599. Each keyboard appears alongside its module version.
THE DARK SIDE
This paragraph, and the next, contains words which you may find distressing, from the start, and throughout. Please skip this section if you feel you might be disturbed by the phrase General MIDI… Oh no, I’ve said it… If you found that offensive, you’d perhaps better leave the page now, because there’s more graphic discussion of General MIDI (oh no, did it again) to come… So, General MIDI was devised as a standard for multitimbral instruments to allot the correct sounds to each part in a MIDI arrangement. A multitimbral instrument simply being one which can play multiple timbres at the same time. Used with a sequencer, it can play, say, a bass sound on MIDI Channel 1, a trumpet sound on MIDI Channel 2, etc. The Korg X5 was 16-part multitimbral, meaning it could produce 16 different instrument sounds simultaneously, each playing whatever the sequencer told them to play. The X5’s 32-note polyphony, however, enforced the same limitations as with the Combi Mode presets.
A General MIDI synth would come with a dedicated GM sound bank, and the X5 conformed to that, offering the GM bank in addition to the regular bank of basic user presets. With the general MIDI bank, the locations of the instrument sounds in the memory were pre-ordained. So Preset No. 1 would always be an acoustic piano, for example. When the MIDI arrangement was programmed, the programmer would specify Preset No. 1 for an acoustic piano part, and the General MIDI instrument would call up its acoustic piano preset in response. In theory, perfect. But in practice, General MIDI became a byword (or phrase) for karaoke city. The problem with such a universal standard was that it couldn’t possibly play to the strengths of the synth. The synth was forced to mimic specific instruments, whether it was capable of doing so or not. Almost inevitably, the synth would not be able to mimic some sounds as well as it did others, and when the poor sounds were automatically selected by the MIDI arrangement, even a good synthesizer could sound like a karaoke machine. For this reason, many musicians can find discussion of General MIDI harrowing, and I’ll now leave the matter alone, having covered the X5’s GM capability.
A DYING BREED
But by the time the X5 had established itself in the shops, trends in synthesis were changing. Glorified digital sample players such as the X5 were waning at the forefront of tech development, and players were moving back towards analogue type synthesis. 1995’s Korg Prophecy started a major new clamour for digital synths which performed as analogues. The big advantage was that analogue-style synths had the scope for warping and morphing the sounds over time, using active knobs on the front panel. Sample & synthesis machines like the X5 had no facility to twiddle with the filter settings on-the-fly, and generally squelch around with the presets in real time. The dance music of the mid ‘90s was highly analogue (or virtual analogue) orientated, and the role of the X5 - essentially a 1980s synth – was now minimal.
Korg did update the X5 to incorporate 64-note polyphony (in the X5D), but it was almost impossible for this ‘80s technology to compete in the desirability stakes with the exciting new ‘physical modelling’ of the mid ‘90s. The Prophecy also incorporated a powerful arpeggiator which made it so easy, and so much fun, to play around with. AI² didn't die overnight, and as I mentioned it was to continue with Korg's N series after the X5, but its days were numbered.
Today, the X5 is probably most useful for traditional keyboard sounds such as harpsichords, electric pianos, organs and the like. The factory presets sound quite dated to me, but there’s plenty of scope to create modern-sounding alternatives which are not so seriously awash with effects. I use the Program Mode as a store for sound components rather than actual presets. Components which can be imported into Combi Mode and united to create patches which do stand up well against the presets on much newer keyboards. For example, I might make an organ drawbar tone in Program Mode, then stack up several of them in different pitches to produce a convincing Hammond or combo organ sound in Combi Mode. The drawbar tone and other ‘component sounds’ can’t realistically be used on their own, so Program Mode is sacrificed, but the 100 Combis really are worth having.
In truth, the X5's multisampling isn’t very good and you can hear the cut-off points pretty plainly in the raw samples. But you can disguise that by layering up the samples, and it has to be remembered that this was never a high-end synth. If you forget all the General MIDI and multitimbral lark, and concentrate on making the most of Combi Mode, you can get the X5 to perform as a much more powerful take on the Yamaha DX7, with the added benefit of built-in effects and more convincing renditions of real instruments. Looked upon in that light, the Korg X5 could appeal to a lot of musicians – especially if they happen to find one going seriously cheap, as is sometimes the case.
There's a look at what Korg were selling immediately before they unveiled the AI² system which took them through from the M1 to the X5 series in The Korg 707 Synthesizer. You may, or may not be surprised by the sound engine this 1987 synth was using.