https://www.newscientist.com/article/2170277-facebook-ai-turns-your-idle-humming-into-a-bach-orchestra-piece/

Whistle a jaunty tune, and artificial intelligence can convert it into the style of a Mozart symphony played by an entire orchestra. Facebook has built an AI that can translate any style of music played on any instrument into a Mozart symphony, a Haydn string quartet, or even a Bach cantata with a full orchestra and chorus.

The system consists of two main parts: an encoder, which extracts the features of the input music, and a decoder, which makes those features match whatever style of music it’s being translated to.