'Muzac Project' was a US psychological warfare operation by the Morale Operations Branch of the Office of Strategic Services (April 1944/May 1945).

By April 1944 the demands placed on the Political Warfare Executive of the UK’s Special Operations Executive had increased to the point at which the PWE had insufficient personnel to produce the quality propaganda 'entertainment' believed to be necessary to hold its target German audience. The Morale Operations Branch, which was the OSS’s counterpart of the SOE’s PWE, therefore agreed to produce entertainment in an operation codenamed the 'Muzac Project', and accordingly recruited Hollywood writers, an eight-piece band, and well known performers such as Marlene Dietrich. The branch opened a music department in New York City, used the services of the J. Walter Thompson advertising agency, and wrote and recorded black lyrics for 312 German and US songs as well as specially created pieces. A day’s typical 12-hour broadcast included news from the fronts, air-raid warnings and bomb damage reports, political commentaries, and German domestic news.

The Reichsministerium für Volksaufklärung und Propaganda (Reich Ministry of Public Entertainment and Propaganda) and the Oberkommando der Wehrmacht each issued repeated warnings to civilians and soldiers not to listen to the Soldatensender Allied propaganda programme. Even Dr Joseph Goebbels, the German propaganda minister, recognised its potentially negative effects, acknowledging that the cleverness of its propaganda was worrying. Soldatensender did not provide only good music, however, for after the 20 July 1944 attempt on Adolf Hitler’s life, for example, it broadcast the names of hundreds of Germans supposedly involved in the plot, seeking to implicate both the guilty and the innocent in order to cause the deaths or imprisonments of Germany’s leadership and intelligentsia. Post-war reports indicate that the Gestapo took Soldatensender reports seriously, and Lieutenant General Omar N. Bradley’s US 12^th Army Group claimed that the station was especially popular and that a good percentage Germans taken prisoner in the summer of 1944 had listened regularly, while similar evidence was obtained from officers at the end of their wits as they tried to prevent soldiers from tuning in the broadcasts, which continued until May 1945. Post-war interrogations revealed that German civilians also regularly followed the Soldatensender West.

An outgrowth of Soldatensender was the 'joker' campaign conducted in 1944 after the fall of Aachen. The Morale Operations Branch resurrected General Ludwig Beck, the former chief-of-staff of the German army, who had been executed after the failed 20 July plot against Hitler but whose death was never officially acknowledged. Broadcast from England, the 'joker' campaign made use of a broadcaster with a voice like that of Beck to claim that Nazi incompetence and amateurism had lost the war and to demand that Germans revolt, kill Hitler, overthrow the Nazi regime and sue for peace, thus saving Germany from total annihilation.

Rumours planted in advance of the broadcasts reinforced the idea that Beck was still alive. The first broadcast, made in October 1944, was picked up in Sweden and reported in other neutral nations. The Nazis, caught completely off guard, jammed the 'joker' campaign’s second broadcast and continued jamming it and many other frequencies every night for three weeks to prevent the return of the 'joker' campaign.

The broadcasts produced consternation among the Germans, but also within the Political Warfare Department for the Nazi jamming not only prevented the return of the 'joker' campaign but also interfered with the transmission of other Allied propaganda programming. This development caused consideration inter-Allied dispute, especially when it seemed that the 'joker' broadcasts had to received prior authorisation from the Psychological Warfare Division. Major General Robert A. McClure, chief of the PWD at the Supreme Headquarters Allied Expeditionary Forces reported that although he had been assured by OSS members that the 'joker' broadcasts had been cleared in principle, he could find no such approval, and warned that the Morale Operation Branch had to abide scrupulously within SHAEF directives and gain prior approval of all operations.