[DeepThought]

You might be able to take a mask that has a good seal and connect a hose to it, but it won't act as a good snorkel unless the person is close enough to the surface.
I don't know at what point it becomes impossible, but water put quite some pressure on your chest and makes it quite hard to inhale air from the surface, even if the person's lung are at 1m depth you might need something to pressurize the air. Try taking a hose to the pool and see how far down you can go and still breath well enough to create music (always wanted to do that but never had the chance).
There are some special bags for cameras/music players for shallow depth (<5), try doing a search for underwater music players.