This is an area that Deezer thinks it can improve upon, and is turning to the use of AI (via Engadget) in which it can listen to a song and judge it by gauging its mood, emotions, and intensity, to help come up with smarter suggestions. It also uses both the music and the lyrics of the song itself to gauge what kind of music it is.
Deezer trained its AI to use raw audio signals and linguistic reconstruction models and a Million Song Dataset that aggregates Last.fm tags that describes tunes. Unfortunately it seems that this particular system isn’t quite ready for prime time just yet so don’t expect to see it deployed in Deezer’s services anytime soon, but it does hold a lot of potential and like we said, could eventually result in smarter playlists and song recommendations.