Calms down the 3yo crowd when they are melting..
We listen to Alvin and the Chipmunks greatest hits cd, and my 3yo son started singing "She loves you" and "Please, please me"... the 2 beatle songs on the chipmunk cd.
So I brought this beatle cd for him to listen to, and really, he can be overtired and melting down, I flip to the beatles and he quites down.
He always, always says, this is the beatles (to whatever song we're listening to) and then the next one is the crickets, and the next one grasshoppers. He has no concept of what "The Beatles" are/were... but this music is ageless.
And I'm delighted to listen to some music that isn't targeted to a 3yo... like Rafi (which he loves) or Laurie Berkner (who he also loves).