Considering White Christmas: The Motion Picture was based on a song Irving Berlin had written more then a decade earlier for another movie (Holiday Inn), it shouldn’t be surprising that Berlin actually borrowed the majority of his score from earlier projects:
• “Abraham,” like “White Christmas,” was also written in 1941 for Holiday Inn.
• “We’ll Follow the Old Man” and “What Can You Do with a General?” both were written in 1948 for the unproduced show Stars on My Shoulders.
• “Snow” was composed in 1950, with largely different lyrics as “Free,” for the stage musical Call Me Madam, but dropped during tryouts.
• “I’d Rather See a Minstrel Show” and “Mandy” were written in 1919 for the Ziegfeld Follies of 1919—and, in fact, “Mandy” was itself a reworking of “The Sterling Moon,” which Berlin wrote in 1918 for Yip, Yip, Yaphank.
• “Blue Skies” was written in 1926 for the stage musical Betsy (and reused in several movies including, of course, Bing Crosby’s Blue Skies).
• “Heat Wave” was written in 1933 for the stage musical As Thousands Cheer (and also reused in multiple films, including Blue Skies).
Berlin did write “Sisters,” “Gee, I Wish I Was Back in the Army,” “The Best Things Happen While You’re Dancing,” “Count Your Blessings Instead of Sheep,” “Choreography,” and “Love, You Didn’t Do Right by Me” expressly for White Christmas.