My sense is that if a song needs that much introduction, or setting-up, then the songwriter didn't do a very good job of getting his/her point accross. Other than the title, I usually don't say much to set up a song, unless there is a phrase in a foreign language for instance. In other words, if you feel compelled to say "This song is about my friend Bob's first lost love." the songwriter didn't make it clear enough, and the performer would be well advised to cut the song from the playlist.