The Stoat & Bear wonder....

[Gn2Dlnd]

I just heard this playing in the background of a Sopranos episode and I had to add an alternate 3:

Dave Brubeck's Take Five

and

Vince Guaraldi's Linus and Lucy (should have been in my original three, but it fell out of my head, Route 66 took its place)
Henry Mancini's Baby Elephant Walk

There are a boatload more, but any of these pieces of music can instantly improve my mood.