Count me into the "What a load of rot" camp. I'm with operator on this one. With the price of a decent tension-meter (Park Tool TM-1) well below the $100 mark, there really isn't any reason not to spring for one. When I was younger and learning wheel-building, the only one generally available was from Hozan. This cost $280 in 1984 dollars. And I'd use one whenever I had access to such.

Learning to 'ting' spokes and what sounds mean on highly variable brands and configurations of spokes off the internet is lunacy.