I use Auria on my iPad and while you can buy in-app effects, they are pretty expensive ($20-$40) in comparison to external effects ($5 -$20). This is a great tutorial on using external effects via Audiobus. Two cool things: 1. You can use any effects app you have and therefore are not limited to the in-app effects plugins; and 2. the original track is not altered so you can add or reduce as much of the added effect as you like. Apparently, it works similarly in Beatmaker 2 which I don't have.