Korg OASYS PCI

Korg's longstanding OASYS synthesis project has finally come to commercial fruition. The original plan, to produce a traditional stand‑alone synthesizer, has given way to a computer‑based synthesis and mixing environment running on a multi‑DSP PCI card. Simon Trask takes refuge with the OASYS PCI...

The roots of Korg's new OASYS PCI card lie in a project begun by Korg R&D in California during the early 1990s. That project, known as OASYS, was begun with the aim of developing a commercial instrument based on synthesis algorithms and architectures created using an in‑house Mac software program called SynthKit in conjunction with a DSP card for real‑time processing. Korg R&D's plans for OASYS were ambitious. They wanted to produce an open‑architecture, DSP‑based instrument that could be reconfigured in software to generate any available type of synthesis, with a front end built around a touch screen and a graphical user interface.

Korg demoed an OASYS keyboard instrument at the Winter NAMM show in 1995 — indeed, this very magazine ran a preview of it in the March 1995 issue — and Korg planned to put the instrument on sale later that year. The OASYS' touch screen and GUI elements did see commercial light of day later that year, but on Korg's Trinity sample‑based workstation synth. However, the OASYS keyboard itself was never brought to market, as Korg decided it would be too expensive to be commercially viable.

Synthesis and effects algorithms developed by Korg R&D using SynthKit have found their way into other Korg instruments, though, namely the Prophecy monosynth, the MOSS expansion boards for the Trinity and Triton workstations, the Z1 multitimbral polysynth, and latterly the Electribes. Meanwhile, the R&D team went on to develop the 1212 I/O PCI multi‑channel audio interface, an audio I/O card aimed at the developing computer‑based MIDI + Audio market. But their original dream of an open‑architecture synth remained unrealised — until now.

Instead of producing a stand‑alone synth like the abortive OASYS keyboard, Korg R&D have gone back to the roots of the OASYS project and developed OASYS PCI. This new product is a PCI card with multiple onboard DSPs which can be reconfigured with synthesis and effects algorithms downloaded from the user's host computer — which also provides the graphical front end, using the supplied OASYS PCI Editor software. And the decade‑long OASYS project will soon come full circle when SynthKit itself is released, allowing OASYS PCI users to construct their own synths.

The Package

The Control Panel for one of OASYS PCI's physically modelled synth patches.

The OASYS PCI package consists of a full‑length PCI card, a CD‑ROM containing OASYS PCI Editor software and associated drivers, and a couple of breakout cables. In order to use OASYS PCI you'll need a Mac computer with a PowerPC processor running OS 8.5.1 or later. Korg recommend a minimum of a 200MHz 604e for stand‑alone use, and a minimum of a 233MHz G3 for use in conjunction with digital audio software. I used a 233MHz G3 for this review, mainly running Cubase VST in conjunction with OASYS PCI, and the computer handled everything without breaking into a sweat. OASYS PCI itself places a light load on the host processor, as the whole thrust of its approach is to put the synthesis, effects and mixing load onto on‑card DSPs.

The OASYS PCI card contains five DSP chips, with a total processing power of 480MIPS (Millions of Instructions Per Second). The first, an 80MHz Motorola 56301, handles audio I/O, mixing, PCI buss communications, and routing between the other DSPs. That leaves the other four DSPs, each of which is a 100MHz Motorola 56303, providing a common pool of DSP power for handling the onboard synthesis and effects processing. Although OASYS PCI is available initially only for the Mac, Windows support will "follow shortly" according to Korg.

Overview

The graphical 12‑channel mixer is used to specify routing, Program and Effects assignment.

Despite its name, OASYS PCI is not just a synthesizer on a card. Appropriately for today's computer‑based music production market, it's essentially a combination of OASYS synthesis and effects and the audio I/O capabilities of the 1212 I/O card. After installation, the OASYS PCI card is automatically available to the Editor software, which provides the user interface to the card's synthesis, effects, mixing and I/O functionality. For audio routing and Program and Effects assignment, this interface takes the form of a graphical 12‑channel mixer with associated Send buss and Output buss windows, while synthesis and effects editing is enabled within the Editor program via virtual Control Panels complete with graphical knobs and buttons. Audio input for each of the 12 mixer channels can be an OASYS PCI synth Program, an audio input from the card's interface panel, or an ASIO audio stream coming off hard disk from a program such as Cubase VST, Digital Performer or Logic Audio. The supplied OASYS PCI ASIO driver provides the audio integration between OASYS PCI and other ASIO‑compatible digital audio software, while for MIDI integration into a computer‑based setup OASYS PCI supports both OMS and FreeMIDI; it also comes with Mac serial port drivers for simple MIDI communication. The v1.0.1 software also adds Sound Manager audio support.

Multi‑tasking

OASYS PCI Programs are containers for synthesis Patches; each can hold one or two Patches, and controls keyboard settings, polyphony, triggering and so on.

OASYS PCI's synthesis functionality is available in the form of Programs, which have to be assigned to Multi mixer channels in order to be playable. However, Programs are just containers for the real substance, which is provided by Patches. A Patch contains a particular synthesis algorithm and architecture; there are 28 of these to choose from in the v1.0.1 software, and the idea is that this list will grow (with this upgrade from v1.0 Korg has already added several new physical models, including flute, trumpet, trombone and vocals). There's also a continuous sine wave Patch, included as a diagnostic tool.

A Program can contain two Patches and their parameter settings, which can be key‑split or velocity‑switched (with overlaps) or simply layered, and detuned and transposed against one another. Other control parameters for each Patch within a Program are pitch‑bend amount, scale, voice‑trigger mode, key priority, and unison detune amount. By assigning two or more mixer channels (and therefore Programs) to the same MIDI channel, you can create further, more complex textures. The Scale option is very neat: you have total flexibility to create any scale you want, working from simple instructions provided by Korg in the User Guide to create a text listing in a standard text document. To make your scale available, you just save the document into the Scales sub‑folder within one or more project folders.

Once you've assigned a Patch to a Program, you just double‑click on its name in the Program window to open up its Control Panel window, where you can edit all the available synthesis parameters and set up any MIDI mod routings that you want. All these edits are stored within the Program, and so by default within the Multi that the Program is assigned to.

A Multi is a snapshot of the complete state of OASYS PCI, storing all the mixer channel settings and Program, Effect and I/O assignments, plus all the parameter settings of the assigned Programs and Effects themselves. You can also save Programs individually, and subsequently drag and drop them from the Catalog window into new Multis. So, for instance, you could have a Program that's an acoustic bass and electric piano split, and assign that Program to a Multi whenever you need that combination of instruments — always assuming, that is, that the new Multi context leaves enough DSP power for it. Of course, once a Program is assigned to a new Multi you can customise it according to the context. Any changes will be stored as part of the new Multi, and again you can also save the individual Program.

Programs also store the insert Effect assignments and edits for the mixer channel they're assigned to; whether or not these Effects are loaded when you assign a Program to a mixer channel is determined by whether or not FX Autoload is enabled for the channel. You can save Effects‑Only Programs, so you can store favourite effect chains for subsequent re‑use independently of Patches. Each mixer channel, Send buss and Output buss has slots for four virtual effect processors — making a total of 48 channel insert, 16 Send and 24 Output insert slots, each of which can be assigned a single OASYS PCI effect. However, as we shall see, the OASYS PCI card's DSP power doesn't afford unfettered simultaneous use of either Programs or Effects, even less so Programs and Effects.

Copying a Program, Patch or Effect setup within a Multi or to another Multi is easy: you just click on the relevant Program, Patch or Multi name in the mixer (or Program window for Patches) and drag and drop it the intended destination. Alternatively, you can use the familiar copy and paste commands. Given that you can have multiple Multi, buss and Program windows open at once within the Editor, copying is not only very easy, it's also very flexible. Another very useful feature when you're constructing Multis is the Catalog window. Programs, Patches and Effects listed in this window can be dragged and dropped to the relevant parameter locations in the Multi and Program windows. OASYS PCI also lets you list your own project folders and associated Programs, Patches and Effects in the Catalog window. Strangely, though, you can't access Multis via this window.

Incidentally, a handy tip if you're doing a lot of Multi setup and copying work is to select Disconnect in the File menu. This puts DSP updating on hold, so you don't have to wait several seconds every time you make a Program, Effect or I/O assignment; when you're done, you select Connect and all the changes you've made will be sent to the DSP in one go, which is a major time and frustration saver.

Calling up a new Multi from disk automatically causes the OASYS PCI to be completely reconfigured. All the new parameter settings and associated synthesis and effects algorithms are downloaded to the card's DSP, which takes a few seconds, during which time the card's outputs are muted. This means that in practice you can't switch Multis during a track. Nor can you switch individual Programs, as this requires the DSP to be reconfigured to the new Program's settings (and to new Effects settings as well if FX Autoload is enabled for the mixer channel that the Program's being assigned to). Any changes to individual Effect and I/O assignments and signal routings will also cause the same muting effect.

Another factor mitigating against Program and/or Effect selection during a track is that different Programs and Effects require different amounts of DSP power. When you assign a Program or Effect to the mixer, OASYS PCI allocates the requisite amount. If assigning a new Program or Effect causes the available DSP resources to be exceeded then the entire output of the card is silenced, until you take the DSP load back to within capacity. You can do this by unassigning the new Program or an existing one, unassigning one or more Effects as needed, or reducing the polyphony on one or more of the Programs. Polyphony isn't assigned dynamically across the Programs; rather, you assign a fixed polyphony to each Program, and this plays its part in determining how much DSP processing is required for the Program (this is common when you're dealing with physically modelled sounds, as is the case with OASYS PCI).

Running Out Of Steam

Korg have included a very useful Resource Monitor window in the Editor software which show

If you're expecting to be able to fill up all 12 mixer channels with a variety of monophonic and polyphonic OASYS instrument sounds, you'll be disappointed — even more so when effects come into the picture. There's no hard and fast figure for how much Program multitimbrality OASYS PCI provides, as it varies according to the models used and the polyphony selected — and, of course, the nature and quantity of effects you're using. But six Programs and below, and averaging around three, would be ballpark figures. Here, for instance, is an example of a Multi I created that used up virtually all of OASYS PCI's DSP power:

• Four mixer channels, all assigned single‑Patch Programs: Beat Box (1 voice), Analog 1 Osc (1 voice), Reed Piano (6 voices), Plucked String (6 voices).
• One insert effect (Stereo Auto Wah) assigned to the Analog 1 Osc channel.
• One insert effect (Overdrive Wah) assigned to the Plucked String channel.
• One send effect (O‑verb XL) assigned to Send buss 1, with one effect send on each of the four mixer channels routed to that buss.
• Everything routed to Master — in this case, OASYS PCI's stereo analogue outs. All other channels and busses turned off.

The demo Multis supplied by Korg to show off the OASYS PCI's Programs and Effects use between one and four Programs, and partially fill the insert effect and/or Send 1 and 2 buss effect slots. The exception is a Multi which has single‑voice drum and percussion sounds across 10 channels, with 5‑band EQ assigned as an insert effect on half of those channels.

The PDF User Guide manual (the only paper manual you get is an Installation Guide) has a whole section given over to Managing Resources, with plenty of suggestions for optimising allocation of DSP resources in greater and smaller ways. Korg have also included a very useful Resource Monitor window in the Editor software which shows you in graphical form the current load on the DSPs. By keeping an eye on this window as you edit Multis you can start to get a feel for how different Patches, polyphony and Effects assignments affect DSP load. Still, get used to seeing the error message "There are not enough execution cycles to play this multi" whenever you make an addition that exceeds the available DSP power!

Recording From Oasys

OASYS PCI's limited DSP power means that users will quickly become familiar with this error message.

If you're using OASYS PCI in conjunction with an ASIO‑compatible MIDI + Audio sequencer and you want to get more OASYS synth sounds running concurrently than the card can handle, there's a time‑honoured workaround that is very easy to implement: just record some of the MIDI‑triggered synth tracks back into your sequencer as audio tracks, optionally with effects processing as well. OASYS PCI makes this very easy to do: you just set the Record Source parameter in its ASIO control panel to Mixer Outputs, mute the tracks you don't want to record, and then record the resulting output from OASYS PCI's mixer into your sequencer. I used this method with Cubase VST, and the integration was very tight, almost as if the two were one program (you can even call up OASYS PCI's ASIO control panel within Cubase). It is, of course, worth keeping the original MIDI tracks and OASYS PCI Programs (including any insert effect settings) so that you can go back to the source material at any time; these can be removed from the DSP pool by setting the Output of synth tracks to Off.

Making Connections

Unsurprisingly, analogue synth emulations appear prominently among OASYS PCI's synthesis algorithms.

The card's necessarily compact physical interface panel, accessible from the rear panel of your computer, has one optical input and one output, each carrying eight channels of ADAT‑format digital audio, together with two analogue ins and two analogue outs via the supplied breakout cable, and stereo S/PDIF input and output, again via a supplied breakout cable (which also includes BNC word clock and ADAT 9‑pin sync in/out connectors). OASYS PCI's digital I/O can operate at 24‑bit, and the analogue I/O uses 24‑bit A‑D converters. ASIO support means that compatible programs can record from and send to the card's ADAT, S/PDIF and analogue I/O connections both directly and via OASYS PCI's mixer with its associated effects functionality.

Routing within OASYS PCI is flexible: you can send up to eight audio streams to the mixer, and up to an additional 12 directly to the card's 12 physical outputs (two analogue, two S/PDIF and eight ADAT). Audio can also flow the other way, from the card's physical inputs either directly into your ASIO‑compatible software or via OASYS PCI's mixer and effects. You can also mix and match both routes. And if you're not into software‑based multitrack MIDI + Audio recording then you can use OASYS PCI with external multitrack audio recording hardware by means of its ADAT I/O. You could, for instance, use OASYS PCI's mixer to add effects to individual tracks from an ADAT‑compatible multitrack device and then output the effected tracks in ADAT format to an external digital mixer, or mix them down with effects to DAT via the card's S/PDIF outputs. If you wanted to add computer‑based stereo audio editing to your setup's capabilities, OASYS PCI's routing flexibility would allow you to mix down eight ADAT tracks to an ASIO‑compatible editor such as BIAS Peak or TC Works' Spark.

Channelling Mixes

So what does the OASYS PCI mixer offer? As already mentioned, it has 12 channels, each of which can be assigned a Program, a mono or stereo audio input from one of the card's input connectors (analogue, S/PDIF or ADAT), or a mono or stereo ASIO streaming input. This ability to accept stereo input on a single channel of course potentially increases the number of mixer channels you have to play with, though you're still limited to a maximum of eight ASIO streams to the mixer. There again, you can always use your MIDI + Audio sequencer to submix more than one mono or stereo track in to the same ASIO stream(s), and hence to the same OASYS PCI mixer channel(s).

In addition to the inevitable fader and level meter, each mixer channel includes solo and mute buttons, a pan knob, and a level knob together with mute and pre/post buttons for each of two mono effects sends available per channel. There are also drop‑down menus for selecting the MIDI channel, the A and B Send busses, and the Input Type and Output for the mixer channel. Each effect send can be assigned to any one of the four available Send busses. The sends are post‑insert, but the pre/post button lets you select whether they're pre‑ or post‑fader. Post‑fade is default, but if you want a lot of effect 'wetness' on the channel you can just switch it to pre‑fade.

Width controls the stereo width of the Send buss output, and works in conjunction with Pan to define the overal stereo placement. Owing to constraints on graphical channel space, Width doesn't get its own knob, so you just place the mouse over the parameter and move it forward and back to increase or decrease the parameter value.

Each mixer channel can be assigned up to four insert Effects, depending on the available processing power. If you want channel EQ then you have to add it as an insert effect (and with 14 EQ Effects available you're spoilt for choice). The Send busses each add an Input Trim setting, and let you select any one of the eight available ASIO streams as an additional input. The Sends provide essentially the same features as the input channels, except that there's no FX Autoload option for Send effects, Autoloading being intended only for Program‑specific insert effects, and (obviously) no send options.

If you set each channel's Output to Master, it will automatically go to whichever stereo output you assign as Master bus in the Output buss window (Analogue, S/PDIF, ADAT 1‑2, ADAT 3‑4, ADAT 5‑6, or ADAT 7‑8). Alternatively, you can 'hard wire' each channel to any one of these six stereo outputs; if you want to route a channel to a single ADAT track, you can pan it hard left or right as required. So there's a lot of flexibility in how you can mix (and submix) to multitrack ADAT. Meanwhile, you can easily reroute any outputs to your selected Master output in the Output buss window by enabling their To Master parameters. You could, for example, select S/PDIF as your Master by clicking on the output's Master button, then click on To Master for each of the four ADAT stereo outputs. However, avoiding To Master if you can is one of the tricks you need to learn for conserving DSP power.

Mixer Automation

OASYS uses MIDI SysEx and controller data to provide dynamic mixer automation and the most extensive MIDI modulation capabilities for Programs and Effects I've ever come across. Every single Program and Effect parameter can be assigned up to two MIDI modulation sources, from a list of almost 40, with user‑selectable modulation amount for each source: the only thing you can't do is modulate the modulation amount. You can see at a glance which Program or Effect parameters in a Control Panel have a modulation source and amount assigned to them, as their names are underlined and coloured red. To bring up a parameter's Modulation Palette window you just click on its name (or Option‑click on the name for on/off buttons).

Each mixer channel, Send buss and Output buss can be assigned to any MIDI channel (from a total of 32, arranged as A1‑16 and B1‑16, if you're using OMS or FreeMIDI). A synthesis Program, of course, responds to notes on the MIDI channel of the mixer channel it's assigned to, and the same applies to the parameters of that Program and their assigned MIDI modulation sources. Similarly, the MIDI channel setting of the mixer channel, Send buss or Output buss that an Effect is assigned to determines the channel on which its parameters respond to MIDI modulation data. What's more, parameter changes made in OASYS PCI's Program and Effects Control Panels can be recorded in real time into your MIDI sequencer as SysEx data for subsequent playback. The advantage of making parameter changes this way is that every parameter is uniquely defined in MIDI terms. You can change the MIDI channel assignment of a mixer channel or buss without affecting playback assignment of SysEx data, but on the other hand all Effect parameter changes recorded this way are slot‑specific — move an Effect to another slot and its SysEx parameter changes don't follow it.

MIDI automation of mixer channel, Send buss and Output buss parameters is much simpler, with preset modulation routings for 11 parameters. Volume, width, pan, mute, solo, Send Levels A and B, Send Mutes A and B, and Send Pre/Post A and B parameters are each pre‑assigned a fixed MIDI controller number, and each mixer channel or buss responds to the relevant controllers on its user‑assigned MIDI channel. As with Program and Effect Control Panels, mixer automation is updated graphically when the relevant MIDI data is received (and you can turn off the graphic updating if you want to save a bit of processing power, or you just get tired of it).

Into The Synthesis

The main selling point of OASYS PCI will be the quality and flexibility of its synthesis algorithms, so let's explore those in a little more detail. Korg have been pioneers in the world of physical modelling synthesis technology and naturally, given its pedigree, OASYS PCI is no exception to this trend. Its flexibility recalls the company's Z1 synth, although its sonic character and quality are different. OASYS PCI's sound is cleaner and smoother; as we've come to expect from Korg, the emphasis is very much on professional sound quality. There are seven categories of instrument Patch: Analog Synth, EP, Guitar, Organ, Percussion, VPM, and Waveguide.

The Analog Synth category provides the largest number of models to choose from: nine in all, including Analog 1 Osc, Analog 2 Osc, and Analog Bass‑Lead. These all provide generous implementations of traditional analogue synth architectures, and are a sonic strength of the OASYS PCI. EP provides just one model, Reed Piano, which is a (very effective) Wurlitzer‑style electric piano, with modelling of hammer, reed and pickup. VPM (Variable Phase Modulation) is FM synthesis by any other name, with a choice of two or four operators, the latter available in various carrier/modulator configurations; the implementations are very detailed and thorough. Guitar provides two plucked‑string and two slapped‑bass models, all with a wealth of parameters to get to grips with, providing plenty of scope for fine‑tuning the sounds.

The three Percussion models are related to the sounds in Korg's Electribe R, and include Beat Box, which in addition to letting you create two electronic percussion sounds à la Roland's classic TR808 also includes a two‑part, 16‑step looping sequencer for those sounds, sync'able to MIDI clock. Organ provides the nine‑drawbar tonewheel and three‑drawbar plus sub‑oscillator organ models from the Z1, both offering plenty of fine control. Finally, Waveguide provides the flute, trumpet, trombone, tenor sax and voice models; again, in each case there are plenty of parameters and detailing to get to grips with. For instance, the tenor sax model includes parameters governing breath pressure, breath noise, reed (including embouchure and damping), growl, and horn (including glide, bell width, bell level, and bore level). OASYS PCI's extensive MIDI modulation functionality really comes into its own with these sorts of modelled instrumental sounds, facilitating the sort of dynamic control of various parameters that's needed, ideally, to bring them to life.

Maximum polyphony for each Patch of course depends on the amount of processing power required for it, and on how much power is available within a particular Multi. For instance, you could assign up to 20 voices to the Analog 1 Osc Patch in a single Program, but that would leave you with virtually no DSP power left for anything else. The same applies if you assign 38 voices to the Z1 Organ or Reed Piano Patch, or just 16 voices to the VPM 4 OP Stack Patch. Of course, many of the Patches require only a single voice or just a few voices at most.

Effects implementation on OASYS PCI is as thoroughgoing, versatile and high in quality as we've come to expect from Korg, if not more so. There are 17 effects categories and around 130 effects to choose from. Categories include Amp & Speaker, Compressor & Gate, Delay, Distortion, Flanger, Pan & Tremolo, Phaser, Pitch Shifter, and of course Reverb (eight types). There are plenty of parameters to edit per Effect, all of them dynamically controllable via MIDI modulation, and as if this collection wasn't enough, Korg's intention is to add more effects.

Final Mixdown

OASYS PCI is an impressive achievement on Korg's part. The company cannot be faulted on the quality and variety of modelled sounds and effects on offer, or on the editing depth and detail provided, or the flexibility and versatility of the audio I/O and mixer routing features, or the ASIO integration with compatible MIDI + Audio software. The open‑architecture approach and the potential of SynthKit in conjunction with OASYS PCI are also exciting, holding out the prospect of a product that will change and grow over time.

On the negative side, however, when I began using OASYS PCI, and was starting out from a synth‑centric perspective, I was dismayed to find the 'not enough execution cycles' message popping up when I'd only put together a few tracks of synth sounds. Much use and time later, I've come, I think, to a more rounded and balanced sense of OASYS PCI's capabilities and strengths, but still there is a lingering disappointment and sense that it's underpowered. Not in the sense of its sonic quality, editing depth and sheer excellence, but in the sense of not being able to do enough of everything I want it to do at once (and considering its high price as well). But that 'not enough' is, er, not enough to undermine all its strengths, and with the tight integration possible with MIDI + Audio sequencers there are workarounds that aren't too frustrating. Ultimately, if you're used to working the computer‑based way and are happy to have your high‑end synth and mixer on a PCI card, OASYS PCI has a great deal to recommend it.