Volume
In the bottom right corner of the GarageBand window is a slider that adjusts the song's output volume. This controls the volume of the song as a whole. To adjust the relative volume of individual tracks, use the volume controls in the tracks themselves.
Monitor the gauges above the volume slider before you export a song. If the red dots at the right end of the gauge are lighting up while the song is playing, your exported song may be distorted by sharp popping noises (know as "clipping"). Decrease the output volume until the red dots no longer light up. For more information on clipping and how to prevent it, see the GarageBand 2.0 - Recording, Editing, & Mixing tutorial.
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Part 2.5: Volume
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