I remember once doing some carol-singing (from books) with an informal conductor who was also a tenor and thus was required to sing as well. As we were singing unaccompanied, we sometimes asked him to drop the pitch a tone or so, as the concert settings are often on the high side. The conductor, who had perfect pitch, found this really irksome: "I'm having to sight-read the tenor line, and now you want me to transpose as well!" For the rest of us, no transposition was required, but for him it was more difficult: when he saw an A on the stave he heard an A in his head, but had to sing a G.

I do wonder, too, whether the way you first learn about music makes a difference to the way you approach pitch. I learned tonic sol-fa for singing, quite early in school, from about 6 or 7 years old. It's a system that is based entirely on relative pitch, and it's the one that I still use in my own private mental systems for storing and recalling tunes (also when playing the melodeon, but that's a whole nother story).

Marje