"In the Mood" is a big band era #1 hit recorded by American bandleader Glenn Miller. It topped the charts in 1940 in the U.S. and one year later was featured in the movie Sun Valley Serenade. In 1999, National Public Radio (NPR) included the 1939 Glenn Miller recording on RCA Bluebird on the NPR 100, the list of "The 100 most important American musical works of the 20th century".