On hitRECord,we use a lot of public domain stuff - images, movies... but we hardly ever take advantage any public domain music. Which does exist! So why don't we use it?
Here's how this collaboration works - choose a song that's in the public domain (some good databases to search are here and here, for starters), and RECord it any way you like. Upload it here, and, as always, re-mix, re-work, and have fun.
Because lord knows the Whiffenpoof Song could use a re-vamp. And yes, that is real and no, I'm not making this up.
NOTE: There are some things you should know about copyright, which have been very kindly laid out for us here.