Conversation so far:
who sings backup with luke bryan on to the moon and back
Co-songwriter Hillary Lindsey added harmonies to the track To the Moon and Back by Luke Bryan.
who has hillary lindsey written songs for
Hillary Lindsey has written songs with or for a number of artists including Michelle Branch, Faith Hill, Martina McBride, Shakira, Lady Antebellum, Gary Allan, Sara Evans, Carrie Underwood, and more.

Question: how many number-one singles
Self-contained rewrite: how many number-one singles does hillary lindsey have