Check out Paul Lamere's talk about playlisting that he presented at ISMIR 2010 (The International Society for Music Information Retrieval has conferences about all this stuff, and Paul founded The Echo Nest, which Spotify later bought):

ISMIR: The International Society for Music Information Retrieval

https://ismir.net/

Finding a path through the Jukebox: The Playlist Tutorial:

https://musicmachinery.com/2010/08/06/finding-a-path-through...

>Tutorial 4: Finding A Path Through The Jukebox -- The Playlist Tutorial. The simple playlist, in its many forms -- from the radio show, to the album, to the mixtape has long been a part of how people discover, listen to and share music. As the world of online music grows, the playlist is once again becoming a central tool to help listeners successfully experience music. Further, the playlist is increasingly a vehicle for recommendation and discovery of new or unknown music. More and more, commercial music services such as Pandora, Last.fm, iTunes and Spotify rely on the playlist to improve the listening experience. In this tutorial we look at the state of the art in playlisting. We present a brief history of the playlist, provide an overview of the different types of playlists and take an in-depth look at the state-of-the-art in automatic playlist generation including commercial and academic systems. We explore methods of evaluating playlists and ways that MIR techniques can be used to improve playlists. Our tutorial concludes with a discussion of what the future may hold for playlists and playlist generation/construction.

The Echo Nest:

https://en.wikipedia.org/wiki/The_Echo_Nest

Paul's blog:

https://musicmachinery.com/

And github repo:

https://github.com/plamere