Wouldn't it be awesome to listen to music together? Some of us are lucky enough to be able to play Spotify over loudspeakers when in the office or when with friends. However, when your boss/colleagues/environment does not allow for this amazing part to your day, it would still be great to listen to music together. Using third party audio streaming tools is rather data-heavy and doesn't work as well as it should.
In comes Host mode. When using Spotify, one could start hosting a party, generating a shareable link that will allow clients to sync their music to what the host is playing. This would further improve the use of collaborative playlists, as it is great fun to build a playlist together with your friends or colleagues, and being able to enjoy it together and at the same time.
This method of synchronization would not require any audio streaming from the host, as data regarding what is being played and at what timestep in the song it is playing is all that is required to be shared between clients. Depending on how accurately this can be done, multiple devices could even be used as loudspeakers, increasing the overall volume of your party.
The audio-less synchronization would also easily combine with free Spotify accounts, as occasional ads could just be played with a higher priority than the party's music, resuming into the stream afterward.