It depends on how deep you want to get into music composition. For me, I looked into Cakewalk music software for many years now and have upgraded to Cakewalk’s Sonar X1. It’s is a little pricey. There are others you can buy if you don’t want to spend that much money. Toontrack can also guide you as well as other forum members. If you downloaded ezdrummer, it should come with a program you can open it with, but you have to follow directions properly.
