The songs featured in the library are made by transcribing the original songs (check out for example Cantaloupe island or Giant steps) so the sound can be as close as possible to each song. It's a "handmade" app! Apart from this, there is the polyrhythmic part of the app, which is the most important here. For each song, we choose the polyrhythmic patterns, basslines and piano comping that sound well when you mix all this stuff together (like for example in the Randomize all function). This is necessary so you can practice polyrhythms in the right context.
We are planning to add new songs very soon and we will keep doing it. However it does take time to make them as good as we want them to be.