Oleg, you'll be my hero forever if you can do this:

[erco]

I suppose that you don't have to turn it on, Nearmiss. Different strokes. However, you most certainly can hear voice, music, and morse, over DF equipment in an airplane in flight. It's not Dolby noise reduced surround sound, certainly, but it's good enough. Modern (?) ADF recievers do a nice job of it, and the DF of the day would have been at least as good.