How can I load up songs to my iPod nano?

I have a similar question. I have an old iPod nano that is low-tech, but a beautiful piece of vintage Apple design. I would love to load up a few songs on it to play on an older speaker with a 30-pin (#oldschool!) connecter.

I am down with the whole streaming thing and love Apple Music's range of available tunes; but I have previously had a lot of mp3s and equivalent files that I would just want to add to this device.

Is there a clever work-around that would let me continue to use your excellent tech in this one instance?