I would have thought that most people have a good sense of frequencies - in that they can tell if a singer or musician is 'off'. The ability to recognise a note and give that note its correct nomenclature is a learned skill and therefore should not be part of a discussion about hearing. I wouldn't know a B flat from an A sharp, by name, unless the difference was demonstrated to me. If a musician (particularly those who play stringed instruments) cannot 'tune' their much beloved device then why (and how) are they playing?
[Rosie] On reviewing my post I think I sort of agree with you.
[Projoy] I'm not sure. Some oriental languages seem to rely on intonation changes for the meaning of various words and phrases - though English does the same to some extent - but I suspect that your comment regarding a 'sliding' scale must be true and would certainly not rely on perfect/absolute pitch, just the variation in such.

[Duj] Pianists can't always tune their instrument, and they seem to get on OK. :)

(Projoy) What I can't understand is why everybody hasn't got it from birth. As I said, it's only a form of memory, like remembering colours. (Dujon) Most people can tell if someone is out of tune, but only relative to some other pitch which is assumed correct. Most people who play a guitar can tune it so that the instrument as a whole is in tune. I have a friend who plays a few tunes (only at home), and plays rather well, and his guitar is in tune with itself but at least three semitones flat. He has a good sense of tuning but none whatever of absolute pitch. I tuned it up for him but he said the strings were far too tight so back down it went.

[Rosie] OK. Why can't you understand that? (PS. I hate to point it out for a third time, but we've already discussed twice why it isn't like remembering colors! Perhaps you remain unpersuaded?)

[Rosie] Perhaps I can help. I have played guitar and sung in very amateur choirs. so I'm not totally lacking in the ability to hear pitch. But I hear lots of other things at the same time. For example, when tuning a guitar I'm often not sure if two strings are at the same pitch because of the different texture of the sound caused by the make-up and length of the string.
The same applies with other occasions. If a man and a woman are singing a duet I could tell you if there was a discord (to my ears), but would struggle to say if they were singing the same note (either an octave apart or exactly) because I cannot separate the pitch of a sound easily from the rest of its character.
Also I find it easy to sing a tune (relative pitch), but have no idea whether I'm singing the same notes as on a previous occasion. It seems to me that the ability to keep or hear a tune in your head does not imply that you remember the actual sound (which would imply that perfect pitch should be possible), but rather that you remember a pattern, which you can then apply to the sound when you remember or sing it.