From the GrainWave web site:
GrainWave has an open synthesis architecture, based upon units called operators. An operator can generate a signal or transform one. Operators are collected into regions which represent individual instruments. One or more regions are contained in a patch. Only one patch at a time is available to be played. GrainWave may be played by using the mouse, the keyboard, and/or MIDI.

GrainWave was designed to be flexible, with high-quality audio output, while still maintaining real-time performance. GrainWave 3 has an output latency of 11.6 ms on any Mac running OS 8.1 or higher. GrainWave can also manipulate an audio stream coming into your computer, with a throughput latency of 23 ms. GrainWave has sophisticated MIDI timing system to ensure a less than 1 ms. of jitter with incoming MIDI events.