Synchro Arts, a software developer based in the United Kingdom, makes no bones about how it is positioning ToolBelt in the audio marketplace. The packaging

Synchro Arts, a software developer based in the United Kingdom, makes no bones about how it is positioning ToolBelt in the audio marketplace. The packaging describes the program as a set of "power processing accessories for Pro Tools."

Contrary to what you might expect from its description, however, ToolBelt is not a TDM or AudioSuite plug-in. Rather, it's a separate application that communicates with Digidesign's Pro Tools or runs as a stand-alone program. ToolBelt may therefore interest sound designers regardless of whether they own a Pro Tools system.

BELT LOOPSToolBelt offers three signal processors: a time compressor/expander, a looper, and a unique audio generator, which extends a segment of audio to generate background sounds without using loops. All of these processors alter the length of an audio segment, extending or shrinking it in different ways.

ToolBelt's input signal flows through all enabled processors, so you can perform up to three types of processing in a series (see Fig. 1). The order of processing is fixed: you can't, for example, pass the signal through the Looper first and then through the TimeMod section.

ToolBelt is not a real-time processor; it operates on one or two channels of audio, which normally come from a mono or stereo selection within Pro Tools. In stand-alone mode, you can open mono or stereo Sound Designer II files for processing. Surprisingly, the program supports no other file format.

ToolBelt's user interface is simple, employing a tabbed single-window design that is more often seen in Windows software than Mac software (see Fig. 2). You click on a tab to activate a page for each processing section. Each tab has a switch for enabling or disabling the corresponding processor, and a small "LED" above the switch indicates whether the processor is on or off.

The buttons at the bottom of the window are visible from any page. The Get Audio button pops you into Pro Tools to select a region or, when ToolBelt is operating as a stand-alone program, lets you open input files. The Reset button sets all parameters back to their defaults. The Spot button initiates audio processing and sends the output signals to designated Pro Tools tracks and locations. The Edit button triggers audio processing without spotting the output.

Once you've set the parameters of the processors, you generate output files via the Edit or Spot buttons. Then you audition the output in ToolBelt or Pro Tools. ToolBelt can use Digidesign's Sound Drivers or the Mac's Sound Manager for playback.

IN AND OUTThe In/Out page (see Fig. 2) displays the names of the input files or regions and includes controls to specify where the output signal should be spotted after processing. The Destination controls select which Pro Tools tracks will receive the output. The Position controls specify where the output region will be located relative to the original Pro Tools region. The Destination and Position controls apply only when ToolBelt is running with Pro Tools.

The Orientation controls let you preprocess the signal. The input signal can be reversed, inverted, or both before it is passed to ToolBelt's DSP stages.

LONG AND SHORTThe TimeMod section is a straightforward time-compression/expansion tool with many convenient features (see Fig. 3). You can enter the amount of compression or expansion as a ratio, a start and end time, a duration, or an amount of change. You can also specify changes in terms of beats per minute (bpm), which is especially handy for tweaking rhythm tracks. Video post-production workers will appreciate the Fixed Ratios pop-up menu, which lets you choose from standard pull-up/pull-down ratios (24/25, 25/24, 29/30, and 30/29).

I used TimeMod to process a number of rhythm tracks containing mixtures of drums, cymbals, and electronic sounds. TimeMod maintained the rhythms accurately throughout its range (50 to 200 percent). Synchro Arts states (with refreshing honesty) that the TimeMod algorithm works best within a range of +/-10 percent of the original. I found this statement accurate; at smaller ratios, TimeMod's fidelity is quite good. Artifacts do start to appear as you approach the limits, especially at expansion ratios greater than 1.5.

ROUND AND ROUNDIn some ways, the Power Looper processor (see Fig. 4) resembles the sampler-oriented loop-editing tools found in such programs as Antares Systems' Infinity or BIAS's Peak. It lets you loop a selected region of audio, change the loop points, define a loop crossfade, and listen to the transition between the start and end of the loop. The main purpose of the Power Looper, however, is to generate multiple copies of a looped segment, for use in special effects, to extend background ambience, and for use in various musical applications. This processor is especially handy when you're working with rhythm tracks.

The Number field (in the top left) lets you specify the number of loop repetitions you want to generate. Alternatively, you can specify a length and ToolBelt will calculate the required number of repetitions. A waveform display area is provided beneath the Number and Length controls. A dotted line in the middle of the waveform display indicates the transition point between the beginning and end of the loop. You can change the transition point by moving the line or by pushing the waveform around with a hand cursor. A zoom function provides a closer look at the waveform, but I still found the display area to be much like the LED waveform displays on many hardware samplers: too small and too restrictive. I would prefer a resizable waveform window that not only lets me zoom in, but also lets me enlarge the display to full-screen size when necessary.

You can audition a one-second region around the transition, or you can easily play the entire loop. If you can't obtain a good transition point, you can smooth things out with the crossfade controls. Unfortunately, you can't change the transition point while you're listening to the entire loop; in this respect, ToolBelt falls short of its competition.

Once the loop sounds satisfactory, you press the Edit or Spot buttons and ToolBelt spits out a region with the desired number of repetitions. To conserve disk space, you can define the loop and generate a single repetition. Spot this back to Pro Tools, then copy and paste as many repetitions of the region as you need. Each copy of the region accesses the same disk data, so almost no additional disk space is used.

OLD AND NEWThe most innovative feature of ToolBelt is the Automatic Audio Generator. This takes brief snippets of aperiodic audio (as short as 0.1 second), and from that produces user-defined lengths of similar-sounding audio without looping or cloning the material.

In soundtrack work, it's often necessary to produce background sounds or ambience-waves breaking on a beach, for example. Sometimes a segment of background material is extended by looping or by pasting multiple copies of the segment into a track. If this is not done artfully, however, the loop can sound obvious.

The Automatic Audio Generator takes a unique approach to creating ambience. It analyzes the characteristics of a source audio segment and generates a continuation of the original that sounds plausible but not repetitive. The Generator finds patterns in the selected audio that it randomly extends into new but similar-sounding patterns. Synchro Arts states that the Generator's processing algorithm is based on Chaos theory.

The Automatic Audio Generator's user interface is nearly identical to that of the Power Looper except for two additional sliders that control parameters called Seed and Tolerance. You select a "core" region of audio in Pro Tools and define a transition point in the waveform display, much as you would for a loop. You then specify the length of the segment you want to generate, set the Seed and Tolerance values, and click the Edit or Spot button. After a bit of number crunching, out comes your ambient sound.

That's the theory, anyway. In practice, the Automatic Audio Generator is tricky to use. The algorithm works best with short segments of aperiodic or quasi-periodic material, such as water sounds, cricket and bird sounds, or crowd sounds. You must be very careful to obtain a smooth transition point. The algorithm treats any discontinuities as part of the original sample and regenerates them in the output, which then produces crackling and popping textures. If you can work within these limitations, however, you can frequently generate textures that are quite useful as background material. (In my experiments, the crickets worked best.)

I also tried music and speech recordings and got some bizarre and interesting results. The Generator altered a drum track in an intriguing way: it somehow preserved the sound of the kick drum, while mutilating everything else.

Because the Generator is such a novel and largely unfamiliar tool, Synchro Arts should provide extensive documentation for it. Unfortunately, the company doesn't. For example, the manual devotes one (uninformative) sentence apiece to the Seed and Tolerance parameters. A small table of recommended (but unexplained) settings is also provided. In effect, you are told to select two arbitrary numbers and hope for the best.

Synchro Arts has promised to provide (on its Web site) more audio examples with notes on how they were produced. However, the company also points out that detailed information may not always be helpful. The nature of the input audio is so varied in terms of level, spectral content, short-term spectral variation, and other parameters that the results for any given setting can be unpredictable when applied to different signals. In other words, a fair amount of experimentation and firsthand experience is required to achieve the software's full potential.

BACK AND FORTHA control panel called Synchro Arts Macros comes with the software to set up communication between ToolBelt and Pro Tools. Synchro Arts provides a default key combination to trigger ToolBelt from within Pro Tools. If you don't like the default, you can define your own key combination from the control panel. During installation you must use the control panel to inform the macro processor where to find ToolBelt. Given this information, Synchro Arts Macros can then activate ToolBelt from Pro Tools and vice versa.

For Pro Tools and ToolBelt to exchange data properly, both programs must be set to the same time-display mode and frame rate. If you violate these requirements (for example, if Pro Tools is set to 29.97 fps drop-frame and ToolBelt is set to 25 fps), ToolBelt won't send its output to the right location in the Pro Tools session and no warning message is provided.

Once you've set the frame rate and display mode, passing a chunk of audio from Pro Tools to ToolBelt is simple. In Pro Tools, you just select part of a region within one or two tracks and then press the magic key combination. The Synchro Arts Macro control panel activates ToolBelt (launching it if it's not already running) and passes along the audio data and region information.

Returning processed audio to Pro Tools is equally simple. On the In/Out page, you designate which tracks will receive the output and where the output will be located relative to the original region. Then you click the Spot key, and Pro Tools is activated with a new audio region at the desired location.

This process has one rather odd restriction: you can't select and pass an entire region from Pro Tools to ToolBelt; you have to select part of a region. You can even select a section that is just one sample smaller than the region itself, but it can't be the whole region. This may be acceptable in many cases, but other times it may not be. After all, regions exist in part so that you can work with clips whose lengths are defined precisely, right down to the sample level. Synchro Arts states that this limitation exists because the ToolBelt macro player works by driving the Capture Region command in Pro Tools, which is grayed out when an entire region is selected. That may be, but the limitation is counterintuitive to Pro Tools users, who think of regions as objects to be operated on as a whole.

SUPPORTSynchro Arts responded to and resolved all of my e-mail questions quickly. One of the company's engineers even made a friendly transatlantic phone call to clear up a problem.

Having said that, my calls to tech support would have been unnecessary had the ToolBelt manual been more thorough. For example, a quirk caused communication between Pro Tools and ToolBelt to fail; it turned out that there was a simple but undocumented fix. (For the record: make sure that you put the Pro Tools display into Waveform mode when working with ToolBelt.) As a whole, the ToolBelt documentation (provided in book and online form) is readable and accurate; it just lacks some important details.

BUCKLE UPToolBelt is a solid utilitarian package, focusing mostly on features that are useful in everyday post-production work. ToolBelt is not, however, an audio Swiss army knife, as its name and $425 price tag imply. ToolBelt's time-processing and looping features, while good, are not decisively better than many competing products, and the program's most original feature, the Automatic Audio Generator, requires that you spend a good amount of time gaining substantial experience with it before it becomes practical to use professionally.

Synchro Arts ought to consider implementing ToolBelt as an AudioSuite plug-in. That would tighten the interface (which is already good) with Pro Tools and eliminate the restriction on full-region selection. It would also eliminate the need for the Synchro Arts Macro mechanism. The company should also consider lowering ToolBelt's price. These improvements-combined with more detailed documentation-would make the product much more attractive to its target audience, the Pro Tools user community.

Nevertheless, if you're looking for a new audio-processing program, I suggest that you visit the Synchro Arts Web site, download the ToolBelt demo, and try it out. If you do audio processing or post-production work, ToolBelt may provide the right combination of tools for your particular projects.

John Duesenberry's electronic music is available through the Electronic Music Foundation. Check the EMF catalog at