“In the Mood” seems to have evolved just like so many other melodies.
We start with "Clarinet Get Away” (Jimmie O'Bryant) by O’Bryant's Washboard Wonders in 1925 for Paramount records, the first minute of this post.

Next is the 1930 recording by BBQ Joe and the Hot Dogs “Tar Paper Stomp” (Wingy Malone).

In 1938 Edgar Hayes recorded what we now know as "In The Mood". This is perhaps the greatest Big Band tune ever!

Glenn Miller's version of "In The Mood" (Joe Garland) rode atop the charts for thirteen weeks in 1940. The next year it was featured in the movie "Sun Valley Serenade" and that is the track heard here.