Whilst this app does sound like it might be an interesting and even useful thing to have around, $19.99 for an app with only this as it’s description (see below) seems a little expensive to me. However, you should as always, make up your own mind.
XII is an “auto-composition” app that generates music with Twelve-tone technique.
This is the piano version.
- real-time calculation
- sequence setup.
- background audio.
- wifi-midi send.
Doesn’t seem like a lot to go on for $19.99, in my opinion.