Sinevibes has released Switch 2.0, a Mac Audio Unit plug-in which they say is specifically designed for rhythmic audio gating. Here's the company's description of Switch...
At its heart is a flexible sequencer that runs in tight sync with your audio signal and controls a series of up to 32 gates with variable duty time and smoothness. It's a simple but versatile effect, capable of applying tremolo, gate, pumping and stutter patterns on any kind of audio material – and it's absolutely essential for every musician.
Switch displays a live audio waveform and aligns its sequencer graphics with it – exactly in the same way it's done by the sound engine, for true "what you see is what you get" operation. Every element in its user interface is color-coded and features subtle animations, bringing unusual ease of use and interactivity. Plus, all this goodness is rendered right on your Mac's graphics adapter meaning fast response and no extra load on the main processor, regardless of how new or old your system is.
Sequencer with up to 32 steps, variable duration, division and swing ratio.
Audio gate with variable duty time, lag and intensity.
Eight parameter snapshots in each preset, available for realtime switching and automation.
Host transport synchronization with support for tempo and time signature changes.
Live input waveform with fluid sequencer graphics that visually match its timing.
Multiple utility functions for copying, looping and shifting individual sequences or whole snapshots.
Support for high-resolution Retina screens.
Works with OS X 10.6 or later.
Pricing and Availability: Switch 2.0 is now available for $29. It's a free upgrade for all users that own the previous version. Switch is also available with a 50% discount as part of the Dynamic Collection bundle ($99) which includes Sinevibes' best sequenced effects such as Cluster, Inertia and Flow.