There is a little exercise you can memorize to help with interval recognition by using tunes to remember the intervals/scale e.g. Twinkle Twinkle Little Star, the first 2 notes are a perfect 5th apart so you can hear it without an instrument, there is a tune for all the intervals in the major/minor scale, also Zeppelins Whole Lotta Love, the first two notes are a minor third apart...and so on.
If you wanted to expand on this.. Twinkle Twinkle as above.. the third note is a major 6th.. within 3 notes you have the root, a perfect 5th and a major 6th, remember to reference everything from the root, and be careful not to do this in public too much especially nursery rhyme songs, people may get the wrong idea
