Simplify the following text for a Grade 9 native English-speaking person.
Original: In connection to Beethoven 's Kreutzer Sonata , Peter Cropper said that A major `` is the fullest sounding key for the violin . ''
Simplified: Peter Cropper said that A major `` is the fullest sounding key for the violin . '' , when he was talking about Beethoven 's Kreutzer Sonata .