How I Use It
I use it mainly in my private lesson settings. I have students create a beat and any other layers they choose. They can have a melody and then try to play it by ear (ear training) or the can improvise a melody to the beat they created.
Garageband is great for teaching musical concepts such as composition, texture, timbre, expression, harmony, etc. It is also good for reinforcing what instruments go together well. It is kind of expensive and a little difficult to figure out how to use at first, but I think it is worth it.