Hark the Herald Porcupines Sing
Amazing catch. Feline Fe was one of the regular commenters on the Everett tweakercam, and she has resumed posting segments from various webcams.
This is from a Texas wildlife cam.
Very few mammals sing a sequence of notes like this. Birds and humans do it all the time for communication and for amusement. This porcupine seems to be singing for amusement. Nobody else is around, nobody to mate with or fight with.
I found a few other Youtube clips of porcupine calls, but they're not musical sequences. They're single downsweeps like a dog's begging sound.