As far as I'm aware this is impossible to develop, but I don't know enough about it.

An interesting thing is that I can recall the starting note of songs in the key they are in, for example, I can recall a 'c4' because that is the first note of Can't Buy Me Love by the Beatles. I am intrigued to know if I could turn this into perfect pitch in some way, through memorising all the notes, or is it too late for me? (I am 30 haha)

can u play piano by thinking of a note

i mean playing piano by ear

I understand that there's another listening skill that Dr. Shawn Wallace from Ohio State University calls True Pitch, which is not perfect pitch, but would give you a similar skill. Saxologic talks about it in his entertaining way on this Youtube video:

I have studied this at some length. First of all, the definition of what perfect/absolute pitch is should be clear. Perfect pitch is the ability to identify a tone without any reference. So this is not the ability to play by ear, nor is it the ability to identify a pitch in relation to another pitch which is known (that would be relative pitch, which can be learned). In fact, nothing on this site requires perfect pitch to be able to do. Perfect pitch should also not be confused with pitch memory either, @Ciarán Buckley mentioned knowing a certain pitch as it relates to a certain piece of music. This is an example of good pitch memory, but not perfect pitch.

All of the credible research would seem to conclude that perfect pitch does not develop past the age of 4-5. There is good evidence to suggest that perfect pitch occurs largely as a result of environmental factors. For example: there are a number of languages in which pitch informs the meaning of words. In these languages there is a significantly higher occurrence perfect/absolute pitch than there are in languages that don't have that characteristic.

Having said all of this, I would argue that a well developed relative pitch ability is functionally more valuable than perfect pitch anyway. The ability to hear musical structures such as harmony, tonality, chord quality, and so on, is what will make a more capable musician. So if you don't have perfect pitch (I don't), please don't let that make you think that you are in any way an inferior musician to those that do. It is simply not true.

Great video!!!! Thanks @Thomas Folks

@David Robinson Excellent explanation.

@David Robinson That's a really helpful explanation. Thank you. :)

It's also nice to have a term for what I can do. Pitch memory. It makes sense haha.