Locate the Mixing ToolsThe mixing tools are an important component to creating songs in GarageBand.
They are located on the left side of the track timeline.
Using the Mixing Tools
The round knob on the left of the mixing section is the Pan knob. This controls the stereo field that the track's sound will come from. If you turn the Pan left, the sound will mainly come out of the left speaker, while turning it to the right will make it come from the right speaker.
To quickly snap the Pan knob back to zero, hold down the Option key and click the knob.
The volume slider controls how loud or soft the specified track will be in the mix. Be careful not to make the volume too loud or it will distort the audio.
When you click the down arrow on the far right side, it will give you access to the automation data bar.