My friend creates all of his music on an iPad using the 'Garage Band" App. His songs are so different from one another and would probably qualify for many different genre descriptions. Would it be appropriate to use "Garage Band" as a musical genre?
No. First off, the term "Garage Band" is also associated with starting bands with low budges so having that as a genre would be confusing. Second is genre meant to show off what type of music the band/artist supplies.
There are many ways to group music like key, time signature, instrumentation which all show something, but trying to extend those to a genre would not make much sense.