PC-packing DJs can assemble massive grooves with Sonic Foundry's Acid, which lets you create songs by dragging and dropping synchronized audio snippets onto a timeline. BitHeadz's Phrazer 1.0.1 is the first loop-based composition tool that attempts to bring Acid's power and flexibility to the Mac. While Phrazer doesn't entirely succeed, it's a step in the right direction.
Phrazer's main window contains a multitrack timeline area and buttons for controlling each track's volume and pan, as well as controls for a composition's tempo, volume, and balance. A Files window lists the 500MB of included grooves and sounds. To audition sounds, click on the file names; to start jammin', drag files to the timeline. You can move sounds forward or backward in time, copy sounds, and add effects.
Phrazer can synchronize several files with wildly differing tempos, and it lets you trigger tracks via MIDI and your Mac's keyboard. Alas, Phrazer drops effects when you copy a track, and it couldn't synchronize files I imported from Acid.The Groove Thang: Drag and drop files into Phrazer to create your groove.