There can be a physical reason for apparent tone deafness which is not that at all but an inability to transfer what's in the head to the voice. After always being pitch perfect, an as yet unexplained condition in the larynx means that accuracy of pitch no longer prevails and my brain knows just before the sound comes out when I'm not going to hit it. So I don't sing out and have become quite paranoid about it.

Medical diagnoses have ranged from reaction to medication to allergy producing a form of asthma. I've certainly gor the cough. A cure is not so far forthcoming. Does anyone know any more about this?