It’s already public that Spotify is working with The Echo Nest to bring better recommendations to its streaming music service, but the latter company’s Paul Lamere has given a demo at the sanFran MusicTech Summit showing how it’ll work. On the surface it’s simple – Spotify users will be able to right-click on playlists and choose “Extend Playlist” to have new songs added based on the tunes already in it. As he explains: “If you want to make a playlist of acoustic hair metal ballads, we”ll be able to do that – we know who the hair metal bands are, and we know what a power ballad sounds like.” Excellent.