With that background comes a method we learned, probably in elementary school. Depending on where you came from you learned one of three methods of interval training:
1. Fixed “Do”
2. Movable “Do”
3. The Number “1”
I learned solfège and it seemed to work well for me. I’m writing this because this topic comes up pretty often when teaching my local class. Some insist that their way is best and what I’ve found is whatever you learned early on is usually the easiest for you.
However, when I’m working with a student who has never learned anything regarding intervals, learning by numbers gets the fastest results, in my experience.
Also, as a working singer across the board, most directors/producers ask for a certain place in the scale, like the 5th, for instance, instead of asking for “So.”
Using numbers centers on scale placement, all depending on which scale the song is written from.
Try singing a scale using the numbers 1-8. Then as a practice, incorporate different scale structures like harmonic minor, or melodic minor, keeping the numbers the same but changing the scale. It’s a process of thinking in a specific mode while you are singing to a place in that mode or scale.
Again, no one method is preferred by everyone. Choose which one works best for you and get the basics down. This will make sight-reading a much easier process for you.