Select a song (or switch to a different playlist or change your browser`s genre/artist/album settings) and Smooth Surfin` will play the track once the currently playing track finished.
Set down the sound volume one notch (Apple + arrow down) and the track will fade out and the next be played.
Smooth Surfin` is a small utility that will allow you to place a song in some playlist or modify the genre of all tracks of the currently playing track.