"In the Moo," a song popularized by the American bandleader Glenn Miller in 1939, was one of the best-known arrangements of the big band era. Miller's rendition topped the charts one year later and was featured in the 1941 movie Sun Valley Serenade. The song is an anomaly to chart purists. "In The Mood" was released in the period immediately prior to the instigation of retail sales charts in Billboard. While it led the Record Buying Guide (juke box list) for 13 weeks, it never made the top 15 on the sheet music charts, which were considered by many to be the true measure of popular song success. The popular "Your Hit Parade" program ranked the song no higher than ninth place, for one week only (1940).