"Das Judenthum in der Musik" (German for "Jewishness in Music", but normally translated Judaism in Music; spelled after its first publications, according to modern German spelling practice, as ‘Judentum’) is an essay by Richard Wagner which attacks Jews in general and the composers Giacomo Meyerbeer and Felix Mendelssohn in particular. It was published under a pseudonym in the Neue Zeitschrift für Musik (NZM) of Leipzig in September 1850 and was reissued in a greatly expanded version under Wagner's name in 1869. It is regarded by some as an important landmark in the history of German antisemitism. Source: Wikipedia (en)