[saaaaaam]

It’s a weird technicality of copyright law. When a human teacher plays a song that is a private performance of a composition. When a computer plays a song copyright law treats this as a mechanical copy of the composition and public performance of the composition. When a computer displays musical notation for a composition that is also a mechanical copy.

Private performance of a composition is permitted under copyright law. Creating a mechanical copy and making a public performance requires a licence from a copyright owner and so without that licence there is, in the eyes of copyright law, a breach of copyright.