Playing back a lot of tracks can place significant load on your computer. You will get the most tracks from a computer with an Intel dual-core processor and 1 GB or more installed RAM. Older PowerPC G5 and G4 computers can be used with Magic GarageBand, but will not be able to play back as many tracks. PowerPC G4 and G5 computers will benefit greatly from having more than 1 GB RAM installed.
GarageBand: Suggested Configurations for Magic GarageBand
The Magic GarageBand feature in GarageBand ’08 is a fun way to mix and match tracks to create your own songs.