The simple answer is, "I don't know." I do agree with you that, when you're talking vintage instruments, there can be significant variances between them, even if they are only a few serial numbers apart. However, you then get into the arguments of how much the player can compensate for the tone and how do certain makes/models get a reputation for something (like, "Yamahas are bright horns"). In the case of a Conn-O-Sax vs. an Eb alto, I think it's both the design and how it's played. It was demonstrated, on another thread, that the Conn-O-Sax (and F Mezzo Soprano) have a bore much more like a Bb soprano and have a mouthpiece that matches. The Eb alto should be darker and fuller for this reason. You could also argue that it's the way the horn's played: you can play the C melody tenor so that it has more of a reedy, bassoonish quality or you can say, "It's just another tenor" and play it as such. With the two Evette-Schaeffer sopranos, for HP vs. LP? I dunno. All I can say is that I could tell a difference and I liked the HP one better. (FWIW, I seem to remember something saying that HP was "better" in some way, but the reason why LP won out was because you didn't have to tighten your strings as much, thus saving wear and tear on your $10 million Stradivarius.) In your experience with the C clarinet, just to support SOTSDOs point (so good he posted it twice), I'd wonder if it's the instrument, not the pitch. Or the mouthpiece. Again, too many variables. I've played all of one C clarinet (which, oddly, was HP), one A and two Eb sopraninos -- ever. Finally, you've got the question of player vs. audience: the player might say that horn X is too stuffy, while the audience can't hear any difference. I can accept that.