D’Alembert co-edited his great project, the Encyclopédie; Grimm was his closest friend. Rousseau, Voltaire (who corresponded for 30 years), d’Holbach, Turgot and Montesquieu were the most noted of other contributors to the Encyclopédie. Rameau objected to its denigration of French music, and entered into a running argument with Diderot as well as Rousseau, who’d written the offending sections. Voltaire and d’Épinay were instrumental in getting Diderot’s imprisonment alleviated. Sterne, Hume, Marmontel, Helvétius and Sedaine were all good friends, while Greuze embodied his ideas of what of a painter should be.