Blue Skies All Day Long

This song has been in my head for at least a week! Composer-lyricist Irving Berlin wrote "Blue Skies" in 1926 for the Broadway show Betsy. Like so many of the best popular songs of that era it went on to become a standard of jazz singers. Here's Ella Fitzgerald doing it in a classic recording. First she sings the main chorus of the song, and then she goes off into one of her signature extended scat improvisations on the tune (scat is singing nonsense syllables in jazz). If you listen a couple of times, you might be able to hear the way she uses the tune as the basis for her improvisation--she just embellishes and adds to the tune, but you can still hear the essence of it. It's sort of (kind of) the same idea as theme and variations, in which you just repeat the original tune with some changes. At the end she returns to the words of the song. The chords played by the band are the same for the scat part as for the regular tune.

Here's another version I like.