John Renwick test drives an internal sound chip synth program for the Atari ST

The first commercially available synthesizers were enormous modular systems manufactured by Moog and Roland, using separate units such as voltage-controlled oscillators, filters and amplifiers, connected together with spaghetti-like patch cords. They could take up an entire studio, but were capable of a tremendous range of sounds which modern synths can rarely match. To save money and space, modern synths usually present you with a fixed voice architecture; say, two oscillators, one filter, one amplifier, one modulation source.

Modular systems aren't limited to this size or structure. Despite the size and complexity of these systems, and their lack of modern facilities such as programmable memories and MIDI, many are still in use - by composers such as Tomita, Wendy Carlos and film soundtrack specialist Hans Zimmer. But if you have a Apple Macintosh or Atari ST, and any of the popular MIDI samplers, Turbosynth gives you the facilities of an analogue modular system on a floppy disk.

Requirements

Turbosynth comes from Digidesign, who specialise in software for samplers. The Macintosh version has been available for some time, but the largely identical Atari ST version, now distributed by Sound Technology, is relatively new. It runs on a one meg ST with double-sided disk drive and mono monitor only, and comes with a decent 90-page spiral bound manual and two disks; the master program and a sample file disk.

You can back-up the master disk, but you will need to insert it in the drive before the copy will run. You can also transfer the program to hard disk, and, as with any software package which deals with sample files, this is distinctly preferable. Having said that, even running from a floppy disk system Turbosynth runs quickly enough so that, unlike other sample-manipulating programs, it doesn't give you the urge to commit suicide while waiting for files to transfer.

Version 1.0 is compatible with the following range of samplers, which for the sake of accuracy we'll give you despite the risk of making your eyes glaze over; Akai S-900/950/700/X-7000; Casio FZ-1/10M; Emu Emax (not SE); Ensoniq Mirage/EPS (non-SCSI); Korg DSS-1 (not SCSI)/DSM-1; Roland S-10/220/50/330/550/MKS-100; Prophet 2000/2002; and anything else conforming to the MIDI 12 or 16-bit sample dump standard. Future updates will be compatible with the Akai S1000 and other more recent samplers.

The drivers for all these samplers are included in a separate folder on the Turbosynth master disk, so it doesn't waste memory by loading them all at once. A chapter in the manual explains the differences between samplers, and how Turbosynth copes with their operational peculiarities.

Concept

The idea of Turbosynth is that is allows you to synthesise pseudo-analogue sounds in the computer, then transfer them to the sampler to be played back without all the hiss and looping problems encountered in making samples of real sounds. Turbosynth also allows you to work the other way, loading samples into the computer, manipulating and mixing them with created sounds, then passing them back to the sampler. The principle is beautifully simple, and it works, but of course it isn't just a matter of clicking a few buttons and getting a MiniMoog sound out.

Turbosynth is fully GEM-based, using the full range of pull-down menus, windows and icons under mouse control, so once you understand the functions of the icons all is very clear. It's just a pity that the section of the manual which explains the function of each icon isn't accompanied by illustrations of each one! Your first step is to choose the default parameters from the Setup menu. These include the MIDI channel, sample playback rate (fixed, eg at the correct pitch for your sampler).

Normalisation (whether or not the sound is boosted to its maximum possible volume without distortion caused by "clipping"), and Preview - you can choose to hear previews of sounds you have created through the ST's monitor, or via a cartridge-port sound playback device such as the Navarone digitiser. The next step is to select the instrument in use from the Sampler menu. Now open a new document window (you can have several open at the same time) and you're ready to make noises.

The System

Turbosynth handles three kinds of files; Document, Sound and Waveform. A Document file is the description of the design of a sound - the modules used to put it together. A Sound file is of course the resulting sound itself, which can be manipulated by Turbosynth before transfer and storage in your sampler, while a Waveform file is used by Turbo-synth's oscillator modules to generate sounds using regular waveforms such as square and triangle waves. You can also modify and save your own waveforms for use by the Oscillator modules. The main display is a window empty except for the jack socket icon representing the audio output, which is the end of every Document.

To the left is a column of sixteen function icons. Four of these are the basic tools - pointer, eraser, information requester and jack plug - which allow you to build up and monitor your sound. Sounds are created by connecting modules together using the jack plug icon. Different modules will accept different numbers of inputs and outputs; you'll soon learn the limitations of the system, but dialogue boxes appear if you try to do something impossible.

The Oscillator is the basic "analogue" sound block. Click on the icon, drag it into the window, and position an oscillator to start off with. Double-click on it to bring up the parameter box, and you are presented with a choice of fifteen presets ranging from simple sines, squares and sawtooths to complex waveforms. Rather than being limited to a single waveform per oscillator, you can arrange a selection of different waveforms across a timeline, and the oscillator will crossfade from one to another.

You can also open the Sample drawer, and take sections of samples to use as oscillator waveforms. Waveforms can also be redrawn, either freehand, or using a number of transformational tools including smoothing, distortion, compression and stretching. This is demonstrated by the demo file TurboTalk, where the waveform of a voice saying "Turbosynth" is cut into sections, ranged across a time-line, and filtered to give a strange robotic effect.

The other main sound-producing source is the Sample module. Here you can load any sample from the demo files given, or from your sampler, and apply a full range of re-looping, zoom, cut-copy-and-paste, reverse, duplicate, and "zero" operations. "Zero" sets the volume of a marked section of a sample to nothing;- useful for eliminating unwanted clicks or hiss. So, you have your sound-producing modules arranged on the display.

You can preview the sound from each module using the Speaker icon, and the next task is to process them using other modules.

Processing

The Amplifier Envelope module determines the volume change of an input, much like the VCA of a conventional synth. It has a number of preset envelopes available, which, of course, you can modify or redraw.

The Filter Envelope module works in the same way, offering a low-pass frequency cut-off of up to 500 Hz. The Spectral Inverter module looks similar, but this inverts the harmonic spectrum of an input, allowing you to use richly harmonic frequencies which are normally above the range of the sampler.

The Delay module has Coarse, Fine and Feedback sliders, and works very much like a conventional digital delay effects unit; by controlling this with a Modulation module you can create phasing and flanging effects.

The Modulator module can modulate an input aganst itself, or against another input. By choosing low or high frequency modulators, you can produce conventional effects such as vibrato, or FM effects such as those used by Yamaha's DX synths.

The Pitch Shifter module is used to produce subtle or radical detuning effects; the Mix slider controls the relative volumes of clean and affected signals.

Other modules, such as the Waveshaper, Stretcher and Resonator, have no immediate equivalents ta analogue synthesis, so it may take some time for you to figure out what they can do. The Waveshaper is a form of modulator which works directly on the basic waveforms; the Stretcher alters the length of a sound, so affecting its pitch; while the Resonator alters the harmonic content. More straightforward is the Mixer module, which accepts all the inputs you have created (up to 32), and allows you to balance their levels before sending them to the Output module. Click on the output jack icon and you bring up an information box featuring sample looping facilities. These allow you to display the waveform of the entire sound, set loop start and end markers, zoom in on the waveform, and adjust the markers until you achieve a glitch-free loop.

Setting perfect loop points is a combination of science and art, but Turbosynth's visual editing aids make it relatively simple to create glitch-free loops. Strange, then, that most of the demo files feature extremely short loops designed to give a clean but boring sustain to the sound. Actually transferring a sound to the sampler is straightforward; just select the ST-Sampler option from the pull-down menu, and watch the samples counting of as the sound is squirted through via MIDI. If there's insufficent memory in your sampler to store the sound, you can opt to truncate it. Of course, you can further edit or enhance the sound using your sampler's particular facilities, then save it to the sampler's disk drive for later use.

One problem you'll encounter pretty quickly is tuning; it's not much good creating a wonderful sound if you don't know what pitch it's at. Turbosynth handles this in a slightly cack-handed way; the manual gives you a table of frequencies and corresponding notes; eg 65.41 Hz is C2. It would be nice if there was some way of automatically generating a range samples, correctly pitched so that you can produce a series of multi-split sounds capable of being transposed over a wide range without "munchkinisation". As it is, the only way is to generate several samples, changing the frequency according to values in the table.

Conclusions

While the demo files aren't as immediately impressive as those of, say, Digidesign's harmonic synthesis package Softsynth, I could never manage to get a decent sound out of Softsynth, while Turbosynth can give immediate and impressive results. The plucked bass, mutant synth and synthdrum demos give a fair idea of what you can achieve, and as you gain more experience with Turbosynth it becomes a really valuable synthesis tool.

Turbosynth has impressed me as one of the most significant MIDI software releases yet. It doesn't just make operating your computer/sampler easier, it actually gives the system astonishing sound-creating capabilities it didn't have before - and that's got to be worth getting excited about.

Product: Turbosynth
Format: One Meg Atari ST with d/s disk drive and mono monitor
Supplier: Sound Technology, (Contact Details)
Price: £180