Continuing with my Valentine to farmer's.
From Dad's notebooks, let's remember communicating with whistles: "Thinking back, and there is plenty to think back to - five brothers and two sisters, I remember Alvin and Leonard mostly being away from home, working for neighbors, usually farm work. If they worked within walking distance and were late getting home in the evening, we'd give the shrill whistle call. This was done by putting two fingers as a trangle on the tip of the tongue and blowing hard. These high notes would carry for miles and if the brother was on the way home, we'd get a whistle reply."
I could never whistle this way. You try it and I'll see if I can hear you.