As sample playback and 'sample + synthesis' (S+S) instruments begin to mature, fixed ROM samples are gradually being replaced by RAM sample memory, especially for the top-of-the-range instruments — Korg's T-series, Yamaha's SY99, Peavey's DPM3-SE etc. Typically this extra temporary storage area can be filled by sending samples using the MIDI Sample Dump Standard (SDS), and so the timbral horizons of the instrument can be considerably widened as you are no longer restricted to the on-board samples.

One approach to exploiting user-loadable sample memory is to use pre-packaged sample libraries, either on floppy disk or CD-ROM. If you don't mind a little more work then you could try sampling a sample library CD with a conventional sampler, or a dedicated sample input unit like Peavey's SX 1U rack mounting module. This is a good way of obtaining high quality samples of acoustic instruments, but it's not so good if you intend to explore more synthetic territory with your S+S instrument. Merely enveloping an existing sample is hardly high-powered synthesis.

For serious investigation into real synthesis power you need some way of producing samples that have never seen a microphone, and that is not too mathematically complex. Resotek's Virtual Wave software is designed to help you put together interesting dynamically evolving sounds which can be used on their own, or be used as the basis for more sophisticated synthesis. Some of the S+S instruments already provide rather tame and uninteresting single cycle waveforms based around the classical analogue synthesis shapes — sine, square, sawtooth, pulse etc. — but what Virtual Wave produces can extend far beyond these simple examples.

Virtual Wave is itself a synthesizer — except that it synthesizes sample dumps, that can be loaded into and played by a sampler, rather than producing sounds directly. It uses a simple but very powerful method to give interesting and unusual sounds: you define the waveshape at up to eight points within a sound (ie. along its time-line), and the program calculates a sound that changes smoothly from one shape to the next. This process is called waveform interpolation, and its main strength is that you can create complex, 'moving' sounds from just a few fixed waveshapes. Pitch and Level envelopes are also provided, to give more control over the resulting interpolated sound, but you could of course use the envelopes inside your sampler or S+S instrument if you prefer.

The program allows you to save the definitions for waves or for a complete sound 'patch', and because all you are storing are the details of how to make the wave, the files are very small (which means you can fit lots on a disk!). Producing the basic waveshapes has many parallels to conventional analogue synthesis techniques. A library of waveshapes is provided, ranging from sine to square and sawtooth, as well as variable width pulse, random noise and silence. You can manipulate these basic shapes in many ways: add or subtract them; splice them together; apply a smoothing filter; change their amplitude with time over a cycle; ramp the frequency up or down in a cycle; alter the phase and many more.

Probably the most sophisticated processing comes from the 'Create' option, which provides Additive Synthesis type facilities without the normal overhead of having to control each harmonic separately — instead you use a set of rules which control a harmonic generator to generate your new wave. You specify things like the range of harmonics, the spacing, phase offsets and attenuation divisors, and then the program works out the resulting waveshape. A frequency plot would have been nice, but this is probably the stuff of future versions. Ordinary additive synthesizers use sine waves to produce Fourier synthesis, but Virtual Wave lets you use any wave as the basis for the calculations, so you can perform Walsh synthesis using square waves, or more esoteric forms using already processed waveshapes. The only penalty for all the calculation that the ST is doing to produce the final output is time — it can take several tens of seconds to work out some of the more complex waves.

This principle of processing and reprocessing can turn the simple geometric library shapes into waves which have much more natural and interesting timbres. You can dump single looped waves quickly via the Sample Dump Standard and hear what each wave sounds like, so you can rapidly get a feel for the relationship between the shape of a wave and its sound (the Peavey DPM3-SE's sample audition facility is very useful for this).

The final stage of processing involves specifying up to five other detuned versions to mix with the basic sound, so you can create chorused or octaved sounds. The 'finished' sounds require still more time to calculate, since the program needs to work out the interpolation between the waveshapes and the effect of the pitch and level envelopes, but because the sound is produced 'on the fly' — the program transmits the data for the start of the sample as the rest of it is being calculated — you can create long samples which are several megabytes in size without lots of memory in your ST. A one second long 16-bit Virtual Wave sample, at 40kHz sample rate, will typically take about two and a half minutes to transfer via the MIDI Sample Dump Standard — you may find that a book or puzzle is a useful accessory.

The program will work at just about any sample rate, with either 12 or 16-bit precision, and there is special provision for Ensoniq and Akai samplers. For rack-mount samplers a mouse-driven 'virtual' keyboard is provided so you can audition your sounds. A wide range of waves and complete sound 'patches' are provided on disk, but a couple of hours of exploration should see you with a new and varied collection of sounds and waves to play with. Purchasers will never be able to complain about static and boring single cycle waves again — they can make their own much more interesting ones with Virtual Wave, just by investing a little time and patience.

FURTHER INFORMATION

£99.95 inc VAT.

Resotek, (Contact Details).