GarageBand allows you to plug in a real instrument and record it as a track on your music project.
Set up a tempo track on your project and open up a new track for recording.
Check the Input Source
Make sure you are using the correct input for your instrument. Go to the Input Source in the bottom right corner and select your instrument's input.
Check the Signal Level
Test play your instrument to check the track signals. You want the signal level to be around the halfway mark. If it is too high or too low, you will need to adjust the gain level.
Adjust the Gain Level
You can adjust the gain level with the slider on the bottom right corner labeled Recording Level.
Record
When you signal levels are correct, press the red Record button at the bottom center.
Play your instrument and it will record on the track.
