An orchestra conductor who performs symphonies by Haydn and Mozart, even by Beethoven, has the right to make additions.

But it is intolerable that the scores should be printed with these nuances and bowings which are in no way due to the author and which are imposed by the editor.
Nevertheless, that is what happens, and it is impossible to tell where the authentic text ends and the interpolation begins.

In addition, the interpolation may be the exact contrary of what the author intended.
This evil is at its worst in piano music.

Our famous teachers, like Marmontel and Le Couppey, have published editions of the classics which are full of their own directions.

But the player is forewarned; it is the Marmontel or Le Couppey edition and makes no pretence of authenticity.