“The model used in today’s Doodle was developed by Magenta Team AI Resident Anna Huang, who developed Coconet: a versatile model that can be used in a wide range of musical tasks—such as harmonizing melodies or composing from scratch.
Specifically, Coconet was trained on 306 of Bach’s chorale harmonizations. His chorales always have four voices, each carrying their own melodic line, while creating a rich harmonic progression when played together. This concise structure made them good training data for a machine learning model.
You can download the midi file”
Source : google.com/doodles