Billie Holiday and Louis Armstrong, "Do You Know What It Means?":
In 1947, the movie "New Orleans" featured a number of jazz greats performing songs interspersed with the rest of the plot. A few of the songs can be found on YouTube, and the best of the lot is this clip of Billie Holiday and Louis Armstrong — along with several other important early jazz musicians — performing "Do You Know What It Means?" It's a short clip, under two minutes, mostly featuring Billie. Check it out:
(Okay, so it's obviously dubbed for the movie, but it's still worth a watch and a listen. I particularly like the sailor leaning against the piano playing the beer; he's a very skilled beer player. For an introduction to the real musicians in the band, watch this clip.)