I'm getting so much out of your videos , thank you so much! This morning I started learning a new song and it started further down the bass clef than I have memorized. After learning some theory from your videos I was able to determine the key and followed the notes up the staff and its amazing how it makes sense some how. I was curious how bad of a habit it is to think of intervals as finger spacing and not necessarily going up by half steps? For example, I've noticed that a Major 5th just happens to be where my pinky would be from my thumb and so on. Maybe you can shed some light, thank you!
Well, from a practical playing perspective, it's useful to get the distances from one note to another "into your fingers." So that's great awareness that a fifth is about the distance from your thumb to pinky. But notice that from C to G is a fifth -- two white keys. And from B to F# is a fifth. A white key and a black key. So it's both -- your fingers have to "know" where the fifth is from any note, and your mind has to "know" what note the fifth of any note is. The physical distances are similar, but not always the same.