Mac music makers using Apple's iLife-extending GarageBand Jam Pack can download an Apple software update that extends the capabilities of the module.
While little detail is known pertaining to the upgrade, GarageBand Jam Pack 1.0.1 (a 540K download): "Installs a number of additional effects presets," according to Apple.
Jam Pack is a separately available add-on kit for GarageBand, which ships as part of Apple's iLife 04 suite. It adds 2,000 new loops in a number of instruments and genres to those available to GarageBand. It also offers over 100 additional Software Instruments, over 100 audio-effects presets and 15 additional guitar amp settings. It costs £69 including VAT.