The question was posed yesterday, by my blind and severely developmentally-challenged 21-year-old student, referring to a mind-changing G that suddenly and only briefly appears in a D minor piece by Bartok. Wanting the note to continue, he simply puts it in for the rest of the piece.
It's what I used to do: If I wanted to hear a sound, I would hold it. If I wanted to add a note (like a dominant to change a diminished triad into a more palatable dominant seventh) I put it in. If I didn't like certain sonorities (like the often low left hand parts in Brahms) I simply left notes out.
Why not?
I became totally immersed in answering his question - probably the most profound question he could have asked, and maybe the most profound he ever did ask in relation to anything. Asking questions is not within his mental capacity. I recognized and identified with its seriousness and spoke to it from my own depth about loss and longing and how this conveys to other people the essence of music.
It was a lesson I will never forget.