Sight-reading at the piano is plenty difficult and many students struggle with it, as do many teachers. The teachers struggle with the difficulty of teaching it and are much relieved when a student shows any sign of fluency.
This is where the wonderful traps set by the likes of Muzio Clementi can exercise their true power.
"You got through that phrase very nicely. Now see, it repeats over here and again over there, so you don't have a thing to worry (i.e., think) about." And off we go mechanically repeating just because we can. (I know that temptation very well; I used to do it myself, thinking it would encourage reading. I have come to believe that it actually discourages reading!)
But, as Rachelle's famous song says, "Just because you can doesn't mean you should." Clementi's wondrously inventive imagination could present elements so clearly as to give the player many opportunities to introduce variation: one note louder than the next, these two bars played against the left hand beat, and so on.
It is the terrible over-edited music teachers' editions that have destroyed all traces of the humor, all invitation to play around with every note.
