[FrankHudson]

I like the 5 minute, make one point , idea as a format.

My 1st guess: the three people who he says all responded that "How could you tell it was out of tune if you hadn't heard the song before" were listening to him more than the music with the attention. In other words, they thought he, a producer with a skilled ear, had detected a different overall musical pitch (as if transposed to a new key, or tuned to something other than A440). In other words, they were listening to him, not with a critical ear focused on pitch and to what he was listening to. Now it's odd that the first person who responded that way was his kid with perfect pitch, but every magic trick works by misdirection of human's perception.

In his telling he says he made the exact fault (a single guitar sting that had slipped flat) clear, but I'm thinking that's his telling after the fact not an exact transcript of how the informal conversations went down.