You just broke my mind. I have visual aphantasia but until I just read your comment about audio aphantasia it never even dawned on me that hearing a song or sound in my head was a possibility. I just did your “who let the dogs out” test and I could remember the tune but as soon as I stopped thinking about it, it went away. That’s a wild personal discovery to have from an HN comment. Thanks!
There's been some great research into aphantasia in the last ~5 years - worth reading about if you have aphantasia.