We can debate how large an obstacle it is, or whether learning to overcome it is valuable, but clearly it is there, even if it's just an annoyance. I just thin

We can debate how large an obstacle it is, or whether learning to overcome it is valuable, but clearly it is there, even if it's just an annoyance. I just think it would be really nice for (e.g.) a clarinetist to be able to sub in on an alto sax part on sight without having to go the extra mental work of "Ah, right, up a perfect fourth --"