AIVA Technologies, where I am currently an R&D Engineer, recently had a major feature release.
Introducing a brand new way to define your own styles: Generation Profiles. This new feature allows you to define your own unique styles of music that AIVA can generate new compositions for. You can get started by either creating a Generation Profile from scratch, or using a pre-made one from the Library, and tweaking all the provided parameters to your liking. Here are some of the musical decisions that you have control over: harmony, melody type & complexity, accompaniment rhythms, how layers synchronise with each other, tempo, dynamic range, and many more.
Here is a preview of the feature. An in-depth video tutorial may be found below: