This summer, Geary Yelton and I evaluated over 200 iOS music apps (available as of July 2017) and picked our favorites. This list is as complete as it can be as of right now, but with new apps released every week, it's impossible to keep it up to date. Case in point, since the issue arrived, PPG Infinite and Intua Beatmaker 3 were released and would have definitely made the list. Look for reviews of those apps in Electronic Musician very soon.
That said, if you're just getting an iPad and/or want to add music apps to your arsenal, this is a comprehensive guide to what's out there right now.
Here's the direct link to the piece: