Heizenbox ($59) is a real-time granular processing VST plug-in for Mac OS X and Windows XP. The key description is real time: every parameter is available for MIDI automation, and a hands-on approach is highly recommended. A demo version that bit-crushes (distorts) the audio every 30 seconds is available from the Heizenbox Web site (www.heizenbox.com).
Heizenbox is easy to use, though mastering its controls takes a little practice. The first step is to hit the Record button and fill its audio buffer. Conveniently, you can quantize record-start and playback-start to various note values at the host's tempo. A handy Touch mode will automatically initiate recording when you click on any of the primary controls — Length, Offset, and Wet/Dry.
The prominent Length and Offset knobs and their associated Division and Repeats sliders are Heizenbox's most important controls. The Length knob sets the grain size, which can be displayed in samples or note values, and the Offset knob sets the scan speed through the audio buffer. When Length and Offset are set to the same value, the buffer plays back as recorded; each grain plays once and the next grain starts where the previous one ended.
However, things get interesting when you don't use the same Length and Offset value. To that end, the Division slider divides the grain size by an integer between 1 and 16, and the Repeats slider causes each grain to repeat as many as 16 times. You can lock the Length and Offset knobs so that moving either one sets the other relative to the Division and Repeats values. Assigning MIDI remotes to those four controls gives you lots of ways to manipulate the grains (see Web Clip 1).
For the timid of finger, Heizenbox has LFOs for modulating pitch and grain size as well as the cutoff frequency of a built-in multimode filter. You can choose from three grain-playback modes: forward, backward, or forward-backward. A Shuffle knob delays alternate 16th notes. A Gate knob sets gating as a percentage of grain size, and a Blend knob smooths things out by crossfading between grains. Granular processing is not exactly a bread-and-butter effect, but it's a whole lot of fun, and Heizenbox does a great job of it.