Was Duke Ellington's 1941 number 1 hit song, which he wrote with Billy Strayhorn. It was the song you listened to in the sound files for the lesson.

I didn't listen to the files in your lesson, so let's list the information we have:

-song composed or performed in 1941

-song written (together with) Billy Strayhorn

-song by Duke Ellington

There is one such song, and it's "take the "A" train" - I think this is the correct answer!