Wolfgang Amadeus Mozart
Mozart's operas are among his greatest works.  He understood people's characters very well and was able to write music which tells us everything about the personalities in the operas.  The three operas in which he set words by Lorenzo Da Ponte: Don Giovanni, Le Nozze di Figaro (The Marriage of Figaro) and Cosi fan tutte each include some very clever ensembles in which several characters are singing at once, each one showing his or her view of the situation.