Intervals
With intervals - at that youtube link, I posted the following comment (below)
Choose the lower note (of the pair of notes) to be the root note (tonic) of a MAJOR scale. Eg E to G, choose E as the reference, as it is the lower note. Then - in the E major scale, goes E, F#, G#. So E to G# spans THREE notes (ie. E, F# and G#), so E to G# would be a major THIRD. But because we want E to G, which is 1 semi-tone less than E to G#, then it's just going to be a minor third. That's one way. And then another way is just by brute force remembering how many notes (including black-coloured ones) are spanning the pair of notes. E to G spans four notes (including black coloured notes), and we just remember the definition - that a span of four raw notes (whatever colour they are) is going to be a minor third interval. A span of 5 raw notes would be a major third interval.
I had to arrive at the above method (in the quotes) myself because those 'geniuses' that write the theory books and most teachers do not explain intervals in a coherent way.
