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Korg | OASYS 88


The Korg OASYS is a workstation synthesizer released in 2005 using a custom Linux operating system that was designed to be arbitrarily expandable via software updates, with its functionality limited only by the PC-like hardware.

OASYS was a software implementation of the research project that ultimately resulted in the OASYS PCI, a DSP card which offered multiple synthesis engines. The original OASYS keyboard concept had to be scrapped because of too high production cost and limitations of then-current technology.

Production of the OASYS was officially discontinued in April 2009. Korg sold just over 3000 units worldwide.

As of November 24, 2009 the latest version of the OASYS OS is 1.3.3a, featuring the following synthesis engines:

  1. HD-1: A PCM synthesizer, with 628 MB of preloaded samples and Wave Sequencing.
  2. EXs: A sample library that works by itself or with other engines. EXs-1 is a set of instruments and EXs-2 is a grand piano.
  3. AL-1: A 96-note polyphonic virtual analog synthesizer (84 notes in previous versions of the OS)
  4. CX-3: A modeled tonewheel organ based on the current CX-3
  5. STR-1: A plucked string physical model
  6. LAC-1: Optional bundle ($249.00) including two virtual analog synthesizers, the PolysixEX and MS-20EX, which are updated models of the vintage Korg Polysix and Korg MS20.
  7. MOD-7: ($249.00) Combines Variable Phase Modulation (VPM), waveshaping, ring modulation, PCM sample playback, and subtractive synthesis in a patchable, semi-modular synthesizer.


HD-1 Program

The HD-1 is a sample+synthesis engine with a two "oscillator" structure. In addition to the two "oscillators," an HD-1 Program contains a Vector Envelope, Common LFO (per-program as opposed to per-voice, similar to the modulation LFOs in some early polyphonic analog synths), two common key tracking generators, KARMA settings, and effects.

HD-1 Oscillator

Each "oscillator" consists of a sample playback oscillator, dual multimode filter, nonlinear "drive" and low boost section, amp, and pan. The sample playback oscillator has four velocity zones, each of which can play a mono or stereo sample or a Wave Sequence. Velocity zones can overlap or crossfade. Korg claims very low aliasing distortion, due to the use of band limited interpolation.

Wave Sequencing

Wave Sequences were first introduced on Korg's Wavestation synthesizer, released in 1990. Wave Sequences allow a single note to play through a list of samples, one after the other, with or without crossfades, with other associated parameters changing for each sample, as listed below. This can create smooth, evolving timbres, or rhythmic effects. Internally, Wave Sequences are implemented by using two voices; voice A plays the first sample, voice B plays the second sample, voice A plays the third sample, and so on. Other synthesizers have featured concepts which are similar in some aspects, such as PPG, Waldorf, and Access Virus wavetables, Synclavier resynthesis, and Ensoniq Transwaves and Hyperwaves.

In the lists below, features new to the OASYS (in comparison to the Wavestation) are noted.

OASYS Wave Sequences include, for each step:

  • The sample to play (mono or stereo)
  • Sample start offset
  • Reverse on/off
  • The length of the step, in milliseconds or rhythmic value
  • The crossfade time into the next step, in milliseconds
  • Crossfade fade-in shape (256 steps, from log to exp)
  • Crossfade fade-out shape (as above)
  • Volume
  • Transpose and fine-tune
  • Two modulation ("AMS") value outputs, to control any assignable parameters of the synthesizer in the rest of the Program (e.g. filter cutoff or resonance, LFO speeds, etc.)

And, for the sequence as a whole:

  • Time/Tempo mode (determines whether step durations will be in milliseconds or rhythmic values)
  • Run on/off (enables and disables programmed durations and crossfades altogether; modulation from other sources can control the sequence directly)
  • Key sync on/off (determines whether each note's Wave Sequence runs independently, or whether all notes sync together for lock-step rhythms)
  • Swing and swing resolution
  • Quantize Triggers on/off (adjusts note start times to match current KARMA/Sequence)
  • Start step and start step modulation
  • End step
  • Loop start, end, and direction (forwards, backwards/forwards, backwards)
  • Loop repeats
  • Note-on advance (increments the start step for each played note)
  • Position modulation (sweeps through the sequence manually)
  • Duration modulation (changes the step durations)
Differences from the Wavestation

Additions to the original Wavestation implementation include time/tempo modes, sample-locked tempo sync, constant-time crossfades in tempo mode, fade-in and fade-out shapes, swing, trigger quantization and key sync, note advance, real-time duration modulation, control of reverse and sample start point per step, and modulation outputs.


EXs is a Korg acronym for "EXpansion Sample". They are sample sounds that come pre-loaded with OASYS. EXs-1 is a sample library with acoustic instruments including guitars, brass, piano, strings, beside others. EXs-2 is a grand piano sampled in each key with 4 velocity levels plus damper. The 1G RAM of OASYS only permits to load 1 EXs at a time, but the user can expand it to have both working at the same time.


EXs3 ($149) includes over 700 MB of brass and woodwind samples, perfect for orchestral and pop productions. Recorded using world-class instruments and players, the collection features piccolo, flute, alto flute, clarinet, bass clarinet, oboe, English horn, bassoon, contrabassoon, soprano sax, alto sax, tenor sax, baritone sax, trumpet, piccolo trumpet, cornet, flugelhorn, trombone, French horn, bass tuba, contrabass tuba, dual-trumpets, dual-trombones, and brass ensemble. Designed to be richly expressive, the samples include multiple dynamics, straight and vibrato versions, breathy and overblown tones, legato, staccato, trills, flutter, growl, sforzando, glissando up/down, falls, doits, voice, breath, attack elements, grace notes, and key noise elements. 128 Programs and 64 Combinations take full advantage of the new sounds.


EXi is a Korg acronym for "EXpansion Instrument". It refers to all OASYS synth models other than the HD-1, including the AL-1, CX-3, etc.

EXi Program

This is the Program structure for playing EXi. It is similar to that of the HD-1, but differs slightly in a few ways, such as:

  • Allows selection of any two EXi for layering or splitting
  • Adds a "Common" step sequencer, shared by all voices in the Program
  • Adds audio input selection for each of the two EXi (currently used by MS-20EX and MOD-7)
  • Adds transposition for each EXi


Virtual analog synth engine.

  • Two main oscillators with analog-style FM and sync
    • Korg claims proprietary anti-aliasing technology, for no audible aliasing over standard 88-note range, with sync (but with drive and ring-mod off)
    • Waveforms: Saw, Pulse, Saw/Pulse, Double Saw, Detuned Saw 1, Detuned Saw 2, Triangle, Square/Triangle
    • Wave Morph and Pulse Width/Phase/Detune
  • Sub-oscillator
  • Audio input
  • Noise generator with saturation and dedicated filter
  • Ring modulation (Ring Mod, AM, Rectify, Clip)
  • Mixer provides modulatable volume and filter A/B pan for osc 1, osc 2, sub osc/audio input, noise generator, and ring mod
  • Per-voice, modulatable Drive (nonlinear distortion) and Low Boost (low EQ)
  • Dual resonant multimode filters, including "multifilter"
    • Multifilter provides two separate sets of gain controls for LB, HP, BP, and dry signals, with modulatable crossfade between the two sets
  • 4 EGs
  • 4 LFOs
  • 2 "AMS Mixers" (modulation signal processors)
  • Per-voice step sequencer


A modeled tonewheel organ based on Korg's dedicated CX-3 organ keyboard. This organ mimics and in many ways enhances the sound of the Hammond organ and Leslie speaker with amplifier simulation and other enhancements.


A plucked string physical model that allows you to pluck, strike, scrape, or otherwise "excite" the string with 16 different "pluck" types, noise, or any of the onboard or RAM-based PCM waveforms.


The optional LAC-1 Legacy Analog Collection($249.00) EXi adds the MS-20EX and PolysixEX virtual analog synthesizers.

  • MS-20EX Runs in demo mode until activated.
  • PolysixEX Runs in demo mode until activated.


The MOD-7 ($249.00) includes six oscillators which combine simultaneous VPM (aka FM), Waveshaping, and ring modulation, plus a PCM oscillator, noise generator, audio input, two multi-mode filters, three 2-in/1-out mixers, and an input main mixer – with a patch panel for routing them together.

Note: The MOD-7 and PolysixEX/MS-20EX plug-ins are only available from Owners must register their Oasys at the site in order to purchase them. This includes providing the Public ID and serial numbers of their unit.


ModelOASYS 88
Engine TypeDigital
Engine8 Engine types
Voices (max)172
Engine Detailed8 engine types: Frequency Modulation, Karplus–Strong, Phase Distorion, Physical modelling, ROM, Sampling, Subtractive, Virtual Analog
Sampler16 bit, 48 kHz up to 1.5 GB
Filter (VCF)Generally there are two multi-mode filters per voice; (low-pass, high-pass, band-pass and band-reject) four-mode filter routings (single, serial, parallel and 24dB mode)
Envelope (VCA)ADSR
FX2 Master, 12 inserts
ArpeggiatorKARMA Engine, Available with the LAC-1 EXi synthesis engine using the PolysixEX
Recording16 track MIDI and 16 track Audio Recorder
Key typeKeys, Hammer action
AudioStereo out, 8 individual outs, ADAT I-O
Extra info40 GB Drive of which the 314 MB "ROM" is loaded at startup. 1GB ram expandable to 2GB. Optionally-loaded 313MB EXs1 "ROM Expansion" & 503MB EXs2 "Concert Grand Piano.
Produced:2005 - 2009
Legend: Obvious Y: Yes, N: No, N/A: Not Applicable
VCO Voltage Controlled Oscillator DCO Digital Controlled Oscillator
LFO Low Frequency Oscillator Sub Sub Oscillator
VCF Voltage Controlled Filter VCA Voltage Controlled Amplifier
Velocity As with a piano, the harder you hit a key, the louder the sound, unlike most organs which always produce the same loudness no matter how hard you hit a key. Aftertouch Pressing a key after you activated it. Channel Aftertouch, no matter which key, it will send a Channel message. Poly Aftertouch, sends the pressure per key instead of the whole channel.
Values for OSC, LFO, Filter, Envelope are per voice unless stated otherwise.

Manuals, patches etc.


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