about perfect/relative pitch - what i do when asked to sing a pitch is match it to a melody/song that i know contains that note. i can also do it when hearing a pitch, and i can tell what it is by matching it to another song. i know that's not perfect pitch, since i have to reference a prior memory to get the note, but does it count as relative pitch if i'm not relying on another sound heard at that time? or am i just good at remembering sounds?
That is not relative pitch, no. It’s more that you’re just very good at remembering sounds! That’s how many people who are not born with perfect pitch can essentially “learn” it, though it’s important to test yourself with a tuner, because often what our mind tells us is a remembered pitch is often a bit off. But if you can train yourself in this and consistently match with a tuner, you can essentially learn perfect pitch.
Now, let’s say you can always remember an E because of some song you know. Then if somebody says, “sing a B,” and you remember the E and then sing the B off of that remembered pitch, then that is relative pitch!