This should be an easy question for the experienced players. 
The comment was made that the D/G melodeon is pitched higher than the C/G.
Can someone please explain where these respective scales fall on the piano keyboard with respect to middle “C”?
I am also curious about the D/A combination.
Thanks
Most G/C melodeons are 3rd button start. This means that on the inside C-row the 3rd button from the chin-end is middle C on the push. On the outer G-row, the 3rd button is G below middle C on the push.
On a D/G box with a 3rd button start, the inside G-row 3rd button is G above middle C on the push. On the outer D-row, the 3rd button is D one tone above middle C on the push. Therefore on a D/G box, the G-row is pitched a whole octave higher than the G-row on a G/C box.
On an A/D box with 3rd button start, the 3rd button on the inside D-row is D one tone above middle C on the push (same as the outer row of a D/G box). The outer row 3rd button is A below middle C on the push. Therefore, an A/D box is pitched one tone higher than a G/C box.
Just for completeness, a C/F box is similarly one whole tone below a D/G box.
Hope this answers your question.
