If you’ve watched any period film from the 1930’s that features a toe tapping dance they were probably playing this song!

In the Mood was composed by Joe Garland and Andy Razaf. The piece was arranged by Glen Miller in 1929 and is his most well known arrangement during the big band era. Surprisingly the song was never a chart topper.  According to Wikipedia, It was the first song ever played by a computer in 1951 by a Ferranti Mark 1 computer at the University of Manchester.