There is a new piano in the house. It has led to a revival of interest in duets and duos in our house. How to come all our piano 4-hands books. The early evening returned to Mozart’s Sonata in B flat major. I play the top; Jean the bottom. She tried out the first three descending notes, bold minims in the key chord. B, F sharp, D sharp. All clear and all wrong notes. I could not see Jean’s hands, but I knew that she had played the right notes. I looked at my music. The 3 minims, but B-flat Maj key signature and the echo of the major triad did not shift. Yet I knew that as soon as we put our fingers on the piano together it would all sound in B-flat Maj. And so it did.

My brain receives an identical signal (admittedly with more overtones from my high notes) but interpreted it as different. The change was caused by the position of my fingers in relation to the piano keys.