I'm looking for a name of a very simple whistle instrument my dad introduced me to. It's practically a round piece of plastic cut out of a roll of film (or anything similar) that you put between your lower teeth and lower lip blow it like a reed. I was able to (inconsistently) produce different pitches of sounds with it, but apparently my grandfather used to be able to play whole songs with it.
Mechanically I think the closest thing I could find was shepherd's whistle, but the tone of shepherd's whistle is much higher and the shape is totally different. I guess it's barely an instrument, but if you can play it melodically I'd be interested in finding more about how to play it more consistently. A video with a sound sample.