The Political Warfare Executive (PWE) and Sefton Delmer, a South African-born British journalist who spoke perfect German, created a network of "black" radio stations that mimicked genuine German broadcasts. The most famous was Gustav Siegfried Eins (GS1), which purported to be run by a patriotic German officer called "Der Chef" who was loyal to Germany but opposed the Nazi leadership.
The genius was in the mix: approximately 80% of the content was accurate news (often better than what Germans received from their own media), with 20% carefully crafted disinformation. Der Chef peppered his broadcasts with salacious stories about Nazi officials' corruption and sexual misconduct, undermining morale and trust in the regime.
Another station, Soldatensender Calais, broadcast popular music (including jazz, which was banned by the Nazis) interspersed with accurate war news and subtle propaganda. It became so popular with German troops that captured soldiers sometimes mentioned it. Delmer's operations also created fake German newspapers, forged letters, and other materials designed to sow confusion, distrust, and defeatism within Germany and its occupied territories.