Christoph Willibald Gluck (1714-87) at the spinet Joseph Siffred Duplessis (1725-1802)

The picture has something of this: people, portrait, elderly, writer, man, theatre, leader, music, sit, musician, theater, wear, opera, administration, singer, poet, jacket.
Perhaps it’s a painting of a man sitting in a chair with his hands on his chest and a green box in front of him with a smile on his face.