In the late 1970s, a simple technology helped carry a revolutionary message across Iran: the cassette tape.

Ayatollah Ruhollah Khomeini, living in exile, recorded sermons criticizing the Shah’s government. 

Supporters smuggled the recordings into Iran, where they were copied again and again and passed from person to person. Thousands of tapes circulated through mosques, bazaars, universities, and private homes.

Cassette tapes were difficult for security forces to control. They were small, inexpensive, and easy to duplicate using ordinary tape recorders. A single recording could quickly become hundreds of copies, spreading messages far faster than authorities could track or confiscate them.

Because the Shah’s government tightly controlled television and radio, these recordings became an underground communication network. By the time protests erupted in 1978 and 1979, millions of Iranians had heard Khomeini’s speeches through cassette players.

Long before the internet or social media, the cassette tape functioned as an analog information network, quietly carrying ideas that helped fuel the Iranian Revolution.