A pupil of mine this evening was having trouble with whole-tone scales. So I suggested we worked them out a note at a time.
'Play a low C', I said. She did.
'Now play the note a whole tone up.'
She apparently did, but the two notes sounded the same. I thought perhaps a spring had gone, so I pressed a few keys. Nothing seemed out of place. I gave the flute back to her, and she tried again. D and C still sounded the same. So I tried the flute. Same thing happened.
At this point, my pupil was staring at the flute. 'What's that inside the foot?' she said.
I saw something white, pulled it out....
.....and it was the cheque for her half-term's lessons, put there by Mum so she remembered to give it to me.
So, next time low notes don't work on your flute, check for cheques.