Then I pulled it out in the living room and really gave it a go. All was well until I hit the upper register...that's when I heard it.
A weird, high-pitched vibrato, as if I were doing breath vibrato on another higher whistle playing alongside myself. I was crushed. Burke makes such good stuff, and here (I thought) I had the one weird anomaly.
I played for a while. Three notes in the higher register consistently created the weird warble.
Now, as C.S. Lewis would put it, I read all the right books. That is to say, the sound was weird enough I began to worry about opening strange rifts in the threads of reality.
That's when I went into the kitchen to noodle some more and the sound went away! The whistle played crystal clear.
There is no ceiling fan in the kitchen.
