@iternabe - My first music language was some hybrid version of solfege that a primary teacher gave us, and I didn't learn notation normally until I was over 50. The teacher pointed to a vertical board and we sang what she pointed to. I was seven. The minor Tonic was La - I think normally these days it's also Do. It is easy for me to "sing your numbers". I was surprised at the b7 b7 part and thereafter because it seems a different version from the song I learned.
When I was given a little organ at age 8, and a little book for adult self-learners, I developed an odd way of reading. I "found Do" (above the last sharp, and the last flat "is Fa"), did end up in the right key (won't explain that one) but mostly kept to music with at the most 2 sharps or flats. I'd "hear" the melody from the page by the way the notes went up and down, and as Solfege. For decades my reading music was hearing it from the page like a singer, and playing what I heard. Later when I got a piano, the only music was a set of sonatinas, which were diatonic so the system still worked. No piano after age 18. It was way, way later that I discovered that I didn't know how to read music in a normal way. I was astonished that people see the notehead on the page, find the corresponding piano key, and then discover what the sound is.
There were a few disadvantages to this, and I retrained into normal piano reading skills over a couple of years (by then in my 60's!). (1) Movable Do is relative pitch. You can be mentally hearing it in F major when it's in Ab major. (2) Music isn't always diatonic. There can also be sudden leaps and such. (3) Chords, unless broken chords or Alberti bass, can't be mentally heard in Solfege at all. (4) The nature of reading piano music, with a relationship between an existing note, and a specific place on the keyboard, is cancelled out.
