I have found the location of the background music files for Windows Photo.
Please be sure to look over the licensing agreement as I am unsure if these files can be used with other programs:
Here is the location:
For some reason I could not browse to C:\Program Files\WidnowsApps I kept getting a security error but if you copy and paste the above location it worked for me
The files that say PREVIEW at the end are the longer version of the sound clip. For Example: