Study for a Portrait of Charles-Claude de Flahaut de la Billarderie (1730-1809) Joseph Siffred Duplessis (1725-1802)

The picture has something of this: people, portrait, man, facial hair, wear, Renaissance, outerwear, veil, music, musician, royalty, indoors.
Perhaps it’s a painting of a man sitting in a chair with a piece of paper in his hand.