API v1, Spotify v 0.9.4.185
I don't seem to be able to append songs to a playlist.
This works:
playlist.tracks.insert(playlist_tracks.ref(playlist_tracks.length-1), tracks_to_append)
This doesn't:
playlist.tracks.insert(playlist_tracks.ref(playlist_tracks.length), tracks_to_append)
fail callback for the latter says " is not a track URI." in err.message