In addition to letting you work with individual tracks, regions, and patches, GarageBand includes a set of tracks that you can use to control different aspects of the overall project.
Master track: Lets you control the overall playback volume of a project, including adding fade-ins or fade-outs. For more information, see Work with the master track.
Arrangement track: Contains arrangement markers, which you can move, copy, and edit to quickly reorganize a project. For more information, see Add arrangement markers and Edit arrangement markers.
Tempo track: Contains the project tempo and all tempo changes in the project. For more information, see Tempo track overview.
Transposition track: Contains transposition events used to transpose parts of a project up or down in pitch. Transposition affects MIDI regions and Apple Loops, and can also affect audio regions. For more information, see Transposition track overview.
Movie track: Displays frames of a movie as thumbnails that are synchronized with the ruler, for use in film scoring. Cuts in the movie can be detected automatically and marked. For more information, see Show the Movie track.
You can use these tracks in the Tracks area, Audio Editor, Piano Roll Editor, and Score Editor. When you show any of these tracks, they appear directly below the ruler.