Un Ballo in Maschera (A Masked Ball) is an 1859 three act opera by Giuseppe Verdi (1813-1901) with a libretto by Antonio Somma.  Initially based on Eug�ne Scribe�s libretto for Daniel Auber�s 1833 five act opera Gustave III, ou Le bal masqu� about the assassination in 1792 of King Gustav III of Sweden who was shot while attending a masked ball, Verdi�s version ran afoul of numerous censorship regulations in Naples, Rome, and France.  As a result, the opera underwent a series of significant transformations and title changes, among which include the eventual change in setting from Stockholm, Sweden to Boston, Massachusetts during the colonial era.  Taking over two years from commission to production, it became one of the most frustrating experiences of Verdi�s career. The aria Eri tu che macchiavi quell’anima (You were the one who stained her soul) occurs near the beginning of the third act, where Renato decides to not kill his wife, whom he wrongly believes has been unfaithful, but instead kill Riccardo, whom he thinks is her lover. Instrumentation: 2.2.2.2: 4.2.3.1: Timp: Hp: Str (4-4-3-3-3 in set): Solo Bar.