I think @votingNNN answered you well. The sharps and flats are because the majority of music stays within the scale -- particularly for the singing monks not in

I think @votingNNN answered you well. The sharps and flats are because the majority of music stays within the scale -- particularly for the singing monks not in front of a piano. So they hear and consider the scale and notes falling outside of that sound wrong i.e. they sound sharp or flat Sharp and flat are only needed when moving outside or between scales, or using "fixed do", like modern western sheet music does with sharps and flats. Here is a discussion of the benefits https://music.stackexchange.com/questions/41764/solfege-fixed-do-versus-movable-do https://music.stackexchange.com/questions/41764/solfege-fixe... For the record i prefer and use a numbered tin kay method like the article (but starting from zero rather than one), because it lets me abstractly consider what im playing, in much the same way as the above article