musicians use numbering systems that are actually far more confused than anything discussed here. how many notes in an OCTave?
"do re mi fa so la ti do" is eight, but that last
do is part of the next octave, so an OCTave is 7 notes. (if we count transitions, same thing, starting at the first zero
do,
re is 1, ... again 7.
the same and even more confusion is engendered when talking about "fifths" etc.