Leonardo Da Vinci left clues to a 40-second musical composition in his painting, Giovanni Maria Pala said in a report from the BBC.
Each loaf of bread in the picture represents a note, he said, which combine to sound "like a requiem".
Alessandro Vezzosi, director of Tuscany's Da Vinci museum, said the theory was "plausible".
The notes make sense musically when the resulting score is read from right to left, following Da Vinci's own writing style, Mr Pala said in his book La Musica Celata (The Hidden Music).
The result is a 40-second "hymn to God" which Mr Pala described as "like a soundtrack that emphasises the passion of Jesus".