In the late 1960s and early 1970s, Tom Donahue helped to revolutionize radio broadcasting in the United States. He is regarded as the "Godfather," if not the "father," of "free­ form" rock and roll radio. In 1967 at KMPX-FM in San Francisco, he introduced the commercial underground radio format, which eventually became Progressive and later Album­ Oriented Rock radio. Known as "Big Daddy," Donahue was an imposing figure. He weighed over 350 pounds; sported a thick, dark beard; and spoke with a deep bass voice. He began his radio programs with the line, "I'm here to clean up your face and mess up your mind."

Donahue got his first disc jockey job in 1949, at age 21, at WTIP in Charleston, West Virginia. He moved to radio stations in Maryland and Pennsylvania and eventually was hired in 1951 at WIBG in Philadelphia, where, in addition to the early 1950s popular tunes commonly heard on the air, he played rhythm and blues and rock and roll music.

In 1961 he moved to San Francisco, becoming a disc jockey at KYA, which had a Top 40 musical format. Working with music programmer Bill Drake, Donahue became a "kingpin" disc jockey at the station after helping to make it one of the top-rated operations in its market. The success of Donahue and the station was attributed in part to the fact that he and other disc jockeys heavily involved themselves with the music they played, often holding meetings to discuss the merits of records heard on the air. This distinguished the KYA disc jockeys from others in the business, who saw their jobs as simply springboards to careers in television or movies and who cared little about Top 40 music.

Donahue's interests grew beyond his air shift and music programming jobs. Together with his partner, fellow KYA radio disc jockey Bobby Mitchell, he operated a small record label, Autumn Records. He employed a 19-year-old disc jockey, Sylvester Stewart (Sly Stone), at soul music station KDIA to supervise the production of records by artists Bobby Freeman, the Beau Brummels, and The Great Society, with lead singer Grace Slick.

In the spring of 1965 Donahue left KYA to devote more time to his entrepreneurial interests. He operated a radio consultant service and published a music tipsheet, Tempo, which kept track of record sales. He also owned racehorses and produced music concerts, including a 1966 performance by the Beatles at Candlestick Park.

By the mid 1960s the Vietnam War and the civil rights movement began to dominate the news, and attitudes of young people on those issues, as well as on sex, drugs, and fashion, began to change. In response, Donahue and Mitchell opened Mother's, San Francisco's first psychedelic nightclub, which featured bands such as The Byrds and Lovin' Spoonful.

Although Donahue recognized that Top 40 music had been dominated by rock and roll in the 19 50s and had developed into a formidable economic industry, he believed it had now stagnated, failing to keep pace with changing tastes in American popular culture. For example, in order to play music by an emerging popular group, The Doors, stations often shortened the 6:50 "Light My Fire" to three minutes, and they virtually ignored "The End," which ran u:35. To be sure, there were in the mid- to late-1960s stations that experimented by playing longer musical pieces; the Pacifica Foundation's WBAI-FM in New York City and Massachusetts Institute of Technology's WTBS in Cambridge were two such stations. In 1966 an alter­ native format was presented on commercial station WOR-FM in New York City. However, the "underground" radio format was extremely rare.

Donahue longed to return to radio to program a station reflecting America's burgeoning new musical and artistic landscape. He envisioned a "free-form" format, where disc jockeys were not constrained to be "boss jocks," constantly upbeat and energetic as they chatted in between two-minute pop songs with silly lyrics and commercials for products promising to control dandruff and acne.

In the spring of 1967, Donahue began contacting FM stations, hoping he could convince one to try the proposed format. He felt it was possible, because in the 1960s FM radio still had small audiences and formats mostly of classical or beautiful music, or else they were simulcasts of an AM station's signal. He discovered KMPX in San Francisco, a poor station that made ends meet by selling airtime to anyone who had money to pay for it. Most of the time the station provided foreign language programming.

Donahue convinced the station's owners to let him on the air as a disc jockey and music programmer, and on 7 April 1967 he went to work with the format he would later call "freak freely" radio. There would be no playing of pop singles. Instead, he encouraged the station's disk jockeys to play music from a variety of formats, ranging from rock to blues, to folk, to folk rock. Cuts could be as long as the disc jockey desired, and talk by the announcers was conversational and unhurried. There would be no announcement of the current time and temperature. And there would be no musical jingles heard, as was the case on Top 40 stations.

KMPX's commercial "underground rock" became an instant success in the San Francisco area. In June of 1967 Chinese language programming was dropped completely, and the "underground radio" format was extended to 24 hours a day. Donahue was soon invited to employ the same format at Los Angeles FM station KPPC.

In November of 1967 Donahue was interviewed in the second issue of the magazine Rolling Stone, where he touted the free-form format and derided Top 40 music as "dead, and its rotting corpse is stinking up the airways." Though Donahue overstated his case against AM radio, the changes he brought to the radio music business did force Top 40 stations to rethink their programming, and in time they added album-oriented groups to their programming lists.

In March of 1968 Donahue and his air staff had a falling out with KMPX management, and they went on strike. They moved to San Francisco station KSAN, where Donahue was hired as program director and later became vice president and ​​general manager. In May of 1972 he participated in a radio special honoring the fifth anniversary of free-form music radio. He began the program with Chinese music, to represent the foreign language show his disc jockeys replaced.

In the early 1970s the popularity of the free-form radio approach waned at commercial stations as managers began to reestablish stricter control over disc jockeys and their playlists.

Donahue was still working as KSAN general manager when he died of a heart attack on 28 April 1975. He was inducted posthumously into the Rock and Roll Hall of Fame in Cleveland, Ohio, in 1996.