title: Spotify API: How to crossfade songs
body: <p>I'm using the Spotify API 11.1.60 for iOS and created successfully an app that can download / play songs from Spotify, download and show the covers, execute searches.  But I can't find a way to crossfade songs. I only can play one song a time.</p>
  
  <p>Does anybody know how to crossfade songs?</p>