i'm a flautist. sometimes i have to play notes called harmonics, where the finger position is the same (i.e. same holes closed off) but you have to vary the air speed so that you can hear the original note and also another note above it in pitch. can anyone explain to me why it is that i can hear both notes? because for some notes in the higher octaves, the fingering is the same as for notes in the lower octave, but i can only hear one note. what's the physics behind it? apologies if that's not very easy to understand - i'm not a very articulate person.