Well... you know, if you're stuck on a desert island and you have to play that tape to get a message that could save you, that's one thing... they'd applaud your savvy ingenuity when you got home.
I would strongly recommend against either approach in real life, assuming one cared about one's tape machine.
[EDIT: as I noted in an edit to my post above, like a dumb ass, I was thinking about
voltage not frequency, but I would nonetheless not be
hugely surprised if changing the AC from 60 to 30 Hz did not have other ramifications.]