In my earlier thread on C music transposition I noted this pair:
- music written in the key of G played on a C whistle will be transposed into sounding in the key of F
- music written in the key of C played on a G whistle will be transposed into sounding in the key of F
And similarly:
- music written in the key of A played on a C whistle will be transposed into sounding in the key of G
- music written in the key of C played on a A whistle will be transposed into sounding in the key of G
and so on with the others …
Why does it not seem to matter in the pairs which is the music key and which is the whistle?
I see some connection to the Doppler Shift others have mentioned where source, observer and medium could be applied to whistle, music and listener i.e. it doesn’t matter which of the source, observer or medium is stationary and which is moving, however, in this scenario the whistle analogy seems to fall apart if one moves each of the three which if it held should yield triplets instead of pairs.
Anyway Physics aside, some kind of easy music theory answer would be helpful.