He is best known for composing the national anthem of East Germany, for his long artistic association with Bertolt Brecht, and for the scores he wrote for films.

After emigrating to North America, she turned into an anti-Stalinist, his sister testified against him and his brother before the House Un-American Activities Committee.

His music became increasingly oriented towards political themes and, to Schoenberg's dismay, more "popular" in style with influences drawn from jazz and cabaret.

[9] Though not written in the twelve-tone technique, it was perhaps the forerunner of a musical art style later known as "News Items" (or perhaps better characterized as "news clippings") – musical compositions that parodied a newspaper's content and style, or that included lyrics lifted directly from newspapers, leaflets, magazines or other written media of the day.

Its content reflects Eisler's socialist leanings, with lyrics memorializing the struggles of ordinary Germans subject to post–World War I hardships.

[10] Eisler wrote music for several Brecht plays, including The Decision (Die Maßnahme) (1930), The Mother (1932) and Schweik in the Second World War (1957).

In New York City, he taught composition at The New School for Social Research and wrote experimental chamber and documentary music.

In 1942, he moved to Los Angeles where he joined Brecht, who had arrived in California in 1941 after a long trip eastward from Denmark across the Soviet Union and the Pacific Ocean.

His Fourteen Ways of Describing the Rain, composed for Arnold Schoenberg's 70th birthday celebration, is considered a masterpiece of the genre.

[15] Eisler's works of the 1930s and 1940s included Deutsche Sinfonie, a choral symphony in 11 movements based on poems by Brecht and Ignazio Silone,[16] and a cycle of art songs published as the Hollywood Songbook.

With lyrics by Brecht, Eduard Mörike, Friedrich Hölderlin, and Goethe, it established Eisler's reputation as one of the 20th century's great composers of German lieder.

In two interrogations by the House Committee on Un-American Activities,[17][18][19] the composer was accused of being "the Karl Marx of music" and the chief Soviet agent in Hollywood.

[citation needed] Eisler's supporters—including his friend Charlie Chaplin and the composers Igor Stravinsky, Aaron Copland[20] and Leonard Bernstein—organized benefit concerts to raise money for his defense fund, but to no avail.

Folksinger Woody Guthrie protested the composer's deportation in his lyrics for "Eisler on the Go"—recorded 50 years later by Billy Bragg and Wilco in the 1998 album Mermaid Avenue.

In East Germany, he composed the national anthem of the German Democratic Republic, a cycle of cabaret-style songs to satirical poems by Kurt Tucholsky and incidental music for theater, films, television and party celebrations.

Eisler's opera project was discussed in three of the bi-weekly meetings "Mittwochsgesellschaft" [Wednesday club] of a circle of intellectuals under the auspices of the Berlin Academy of Arts beginning on 13 May 1953.

On 6 September 1962, he died of a fatal heart attack[27] in East Berlin at the age of 64, and is buried near Brecht in the Dorotheenstadt cemetery.