KORG WAVESTATION SR - PCM Workshop

The wave sequencing
This type of synthesis was exemplified, in different forms, by the Fairlight CMI, the PPG Wave series, the Sequential Circuits Prophet VS, and the Yamaha SY22, which was designed by the Sequential team for Yamaha after Sequential's demise. At the end of our last exciting episode, the ex-Sequential personnel had parted company with Yamaha and had been taken under Korg's wing instead, where they continued to develop their concepts further with the Wavestation.

Crossfade to wave sequencing
The transition from waveform to waveform in Sequential's Vector Synthesis, first seen on the Prophet VS, was a simple crossfade, and although two of these crossfades could be controlled or programmed by the joystick which was so integral to the Vector Sythesis system, the maximum number of waveforms which could be involved in a single sound was four. However, the San José-based team's next development -- termed Wave Sequencing -- allowed up to 255 different waves to be involved. This innovation was introduced on the Korg Wavestation, which still featured joystick-controlled Vector Synthesis, but added the much greater potential for transitional synthesis that wave sequencing gives.

The closest precursor of wave sequencing was the PPG system of wavetable synthesis, where related single-cycle waveforms were stored in a group of 32. The user could pick a starting waveform and then use an envelope or LFO to move around in the wavetable, causing timbral changes as the waveform being read out changed. Differences between adjoining waveforms were fairly slight, so the degree of timbral change was determined by how far and how fast the readout moved from the original starting point.

In the case of wave sequencing, coming 10 years after wavetable synthesis, there was much less economic restriction on memory for storing waveforms. As a result, instead of access being limited to 32 single-cycle waveforms, full PCM samples were available, and up to 255 could be 'on-line' for use by an oscillator in a sound. Each stage in the wave sequence could be occupied by a PCM sound radically different from the one before or after it in the sequence. The potential for striking sonic change is therefore much greater in wave sequencing, especially since the PCM waveforms can be deliberately moved around by the user to contrast as much as possible with their neighbours.

PCM Loops : a step in the right direction
The Ensoniq VFX, while not offering the flexibility of wave sequencing, can give you a taste of the possibility of using a string of PCM waveforms as part of your sound. Although you cannot determine the order of the PCM sounds, which is strictly governed by the order in which they were loaded into ROM by Ensoniq, you can set the sample from where the string of samples starts reading out and how many samples will be included. There's no potential for looping each individual sample and setting how long it lasts, let alone crossfading between one sample and the next, but it is possible to set the string of selected samples to loop. Looping allows you to start to create rhythmic patterns which can be used either as the basis for a patch, or as an element to fade in and out via an envelope. As the percussion samples are all stored together, it's quite often possible to find some really neat loops in this area of ROM. Some of the areas with brass and woodwind samples produce loops which sound like the worst sort of avant-garde jazz, but by messing around with the start point and the number of steps in the loop, you can come up with some unexpectedly musical results, especially if you want to create sounds which evolve and change their fundamental nature over time.

Not only can the number of steps in the wave sequence be up to 255, but at each step the user is also able to determine not only the PCM or single-cycle waveform that is to be played, but also the duration of that wave and of the crossfade to the next wave. As a result, a greater degree of fine-tuning is possible than in any preceding form of transitional synthesis. Of course, this also means that it can take a great deal of time to create a really complex wave sequence.

The cycling of the steps still does not exhaust the possibilities of wave sequencing. Once the wave sequence is set, complete with crossfades and loop if required, the point at which playback of the wave sequence starts can be controlled by a variety of modulation sources. These include velocity, which can be set up so that harder keystrokes start playback from early in the wave sequence and gentler ones later on. This technique can be used with wave sequences which include harsher, brighter wave "The real power of wave sequencing is that timbral changes can be as sudden or as gradual as you like." forms in the early steps and softer timbres in the later ones, to create a natural increase in harmonic content on faster keystrikes and a gentler sound on a lighter stroke. Alternatively, you can set a dynamic modulation source like mod wheel or aftertouch to change the step number of the wave sequence. In this case a start step is specified and this stage of the wave sequence is held until the modulation source is activated. Then the movement within the wave sequence is controlled by the mod wheel or aftertouch, so that timbral changes can be introduced as a real-time expression factor. It is this type of facility which makes wave sequencing such a powerful form of synthesis, especially for lead synthesizer work.

More fun with the waves
Wave sequencing is only one of the techniques available on the Wavestation synthesizers. The instrument can be reduced to the simplest of analogue-style architecture, with just one or two oscillators playing back single-cycle waveforms through standard subtractive synthesis filters, but complete with specialist analogue techniques like Hard . However, the number of oscillators can be set to four, and then they can be mixed, either in the normal way, or by using Vector Synthesis via a live joystick or the Mix Envelope, which stores this two-dimensional mix as an envelope over time. Add to this the fact that any or all of the four oscillators can be set to play back wave sequences with their own filters and envelopes and you can see how complex each Patch can become (if the programmer has the time to set it all up). And since the Wavestation is multitimbral, it's possible to combine up to eight Patches into a Performance or 16 Patches on different MIDI channels in a Multi. At Patch, Performance or Multi level, the entire sonic result is passed through two effects, which are as good as those available on any synthesizer at the time .

Although the sales of the Wavestation series of synths never challenged the success of straight PCM-based machines such as the Korg M1 or its successors, as many other people , I would now declare the Wavestation to be one of my favourite Korg synth. It certainly has the potential to be an inexhaustible source of inspiration for real synthesis, allowing access to traditional subtractive synthesis, vector synthesis and wave sequencing.

The PCM Workshop

For a long time, the Wavestation range only depended on their internal ROM available for Wave Sequencing. The Wavestation SR (the latest type issued by Korg after the Wavestation, Wavestation EX and Wavestation AD) takes benefit from the Korg 01W technology used for reading of optional Wave PCM Data Cards. A software has been developped later when the Wavestation production was ended to help musicians in making their own PCM cards. This software permit to compile binary files into PCMCIA Cards. These files, once stored in the PCMCIA card, can be read on the Wavestation SR and Korg 01W instruments only.

"PCM Card Workshop" is the actual Windows program that allows one to add aproximately 33 seconds of new sample data into the synth : The maximum amount of RAM that can be read via the Wavestation SR PCMCIA Slot is 2Mb. The maximum frequency reading is 31.25KHz and the resolution is 16 bits in mono format. All Wave files can be compiled once they are saved in a PCM intel format.

The studio integrates this very interesting feature. Few PCM cards in hands, I can build my sounds and wave sequences into the Wavestation using any kind of external samples...

 

Wavestation Compare-O-Matic
This chart shows the major differences between the four Wavestation models, at a glance. The Wavestation SR look very small (only 1U rack) and very simplified compared to its predecessors. But its the most advanced one in the Wavestation family in terms of sounds storage, effects routing and considering the PCM Workshop facility.

	Wavestation	EX	A/D	SR
PCM ROM	2 MB	4 MB
# of Samples	365	484 (adds piano, drums, sax, more VS waves, etc.)
# of Effects	49	55 (adds vocoders, compressor, pitch shift)
RAM Banks	2		3
ROM Banks	1			8
PCM Card Type	M1-style			01/W-style
# of Multisets	16			32
Display	64x240 Graphic			2x16 Text
Pedal Inputs	Yes			No
Joystick	Yes			No
Latest OS	1.28*	3.19	1.25	1.15
Special Info	*Upgradable to 3.19, without EX PCM	ROM Program card with sounds featuring the new EX PCM	Analog Inputs, Balanced L/R Outputs	MIDI Pan, Multiset Names, Multiset FX Bus settings