librettist

/lɪˈbrɛtɪst/
noun
  1. A person who writes the text (libretto) for an opera, musical, or other long vocal work.
    • She is a famous librettist who has written words for several Broadway musicals.
    • The librettist revised the dialogue to make the characters more relatable.
    • The librettist worked closely with the composer to create the opera's story and lyrics.