I have been playing guitar for over 10 years now, and for more than half of those years I have studied under a tutor in order to force myself to learn new techniques and genres of music (everything from metal and jazz to classical and funk). As such, I have developed a very good ear for telling scales apart and I am pretty good at knowing intervals apart when I hear them.
However, I am unsure if I have developed relative pitch or if I can just picture scales in my head and visualise which notes of a scale are being used. For example, I have no trouble identifying and recreating riffs and melodies on a guitar and after thinking about it a bit, I can work out what theory is going on "under-the-hood" if they use scales I am familiar with; I can also work out what chords are being spelled out in a song if I recognise the chord and with a lot of thinking can recreate the chord if I am unfamiliar with it. But when I hear a line that uses a scale I am not familiar with (non-standard modes come to mind) or an arpeggio I have not heard before, my sense of being able to recreate that melody on the guitar goes out of the window and I have to think for much longer about what is going on in the melody theory-wise.
I have also studied classical theory for a number of years and know (or can work out if I forget) the names of all standard intervals, and know where each note comes in relation to the last (e.g. there is no
F without being pedantic about quarter-tones), meaning I can work out how far apart two notes are when I hear them. Is this relative pitch?
Where is the line drawn between having good relative pitch and just having a good mental library of scales, arpeggios and music theory?