This is another obvious choice. ThumbJam is an app I’ve been using since the day it came out. It’s excellent in its simplicity and elegance. I know for a fact that it is used in so many contexts in community music and in education too and it’s much loved as well.
It is one of the first and probably best examples of an app that is also a digital instrument in its own right. I use it often and it always works well and delivers great results.
So for so many reasons, ThumbJam is right up there in my 24 apps of this year.