Q. My script is a musical drama about a band. I'm no songwriter, but the one original song in the movie has meaning for the two main characters. Should I try to write the lyrics, or just put the meaning and purpose of the lyrics into the script?
You can do it either way. In BUTCH CASSIDY AND THE SUNDANCE KID, William Goldman puts in a lot of hype about how wonderful one particular song is, how haunting and how lovely. He didn't put lyrics, and somehow it wound up being "Raindrops Keep Falling on My Head."
No one expects you to be a songwriter. We have songwriters for that. And there's a good chance that the lyrics won't "read" very well. They rarely do without the music attached.
(However, if you do write the lyrics, you have a shot at a Grammy.)
If your band isn't playing an original song but covering a known song, I'd stay away from naming the song and writing in the lyrics. Readers may not have the same reaction to a given song as you do, so you're better off saying "a haunting love song," and telling us the characters' reactions to it, rather than hoping that "You've Lost That Loving Feeling" is your reader's favorite love song, too.