I find yours a very confusing way of saying it. Hard to parse. As a way of explaining to someone who didn't already know it would be useless, I imagine. The point[0] is:
Instruments in Bb: They play what they call a "C" and it's actually a Bb. To produce a C they have to play a "D".
Instruments in Eb: They play what they call a "C" and it's actually an Eb. To produce a C they have to play an "A".
[0] I only bother writing this because the wrong thing has been written on this page a few times, and not corrected so far.
I find yours a very confusing way of saying it. Hard to parse. As a way of explaining to someone who didn't already know it would be useless, I imagine. The point[0] is:
Instruments in Bb: They play what they call a "C" and it's actually a Bb. To produce a C they have to play a "D".
Instruments in Eb: They play what they call a "C" and it's actually an Eb. To produce a C they have to play an "A".
[0] I only bother writing this because the wrong thing has been written on this page a few times, and not corrected so far.