Robert "Bob" Ostertag (born April 19, 1957) is an American musician, writer, and political activist based in San Francisco.

Musically, he is known for his politically charged compositions created from found sound (Sooner or Later, All the Rage), his work with synthesizers over 45 years (from Bob Ostertag Plays the Serge 1978-1983 to Wish You Were Here in 2016), and his many collaborations (Anthony Braxton, John Zorn, Fred Frith, Justin Vivian Bond, Shelley Hirsch, and Roscoe Mitchell to name just a few).

Thirty-six years later, Ostertag's student work with the Buchla was remixed by techno DJ RRose and released under the title The Surgeon General.

In 1978 he dropped out of Oberlin to tour Europe with Anthony Braxton's Creative Music Orchestra, which had just won the 1977 DownBeat Critics' Poll Album of the Year.

Later that same year, Ostertag relocated to New York City, where he befriended John Zorn, Fred Frith, Zeena Parkins, Ikue Mori, Wayne Horvitz, Toshinori Kondo, and numerous other musicians interested in collaborative improvisation.

Ostertag was not the first musician to perform live with a keyboard-less modular synthesizer, but he was the first person to make it his main instrument in the context of free improvised music.

Here Ostertag played an "instrument" of his own creation involved three reel-to-reel tape recorders, an audio mixer, and six helium balloons.

Following the release of Getting a Head, Ostertag became the first of his generation of musicians to have his work presented at The Kitchen, at the time New York City's premiere venue for new music.

Ostertag eventually became an expert on the political crisis in Central America and published widely for a diverse range of publications, including Pensamiento Propio (Nicaragua), Pensamiento Critico (Puerto Rico), The Guardian (London), the Weekly Mail (South Africa), Mother Jones and the NACLA Report on the Americas (US), AMPO (Japan), and even the clandestine theoretical journal of the New People's Army in the Philippines.

He alternated his time in Central America with organizing and public speaking in the US, giving lectures at Harvard, Yale, Princeton, Rutgers, and many other schools and institutions.

The German newspaper Die Zeit said, "Bob Ostertag did not simply create a political piece but a musical reality, in which sampling technology is used in a significant way for the first time.

When David died before the collaboration could take place, Ostertag made a second, solo piece from the riot recordings, Burns Like Fire, and dedicated it to Wojnarowicz.

New York Times critic Bernard Holland wrote: "Bob Ostertag’s All the Rage turned the evening on its head with a devastating roar of gay anger.

Commissioned by WDR 3 open: studio akustische kunst in Köln, the work was a collaboration with Theo Bleckmann, Shelley Hirsch, and Phil Minton (voice), and Roscoe Mitchell (reeds).

50 minutes of thought, weirdness, and formal precision.” Of all Ostertag's project, perhaps the most unlikely was PantyChrist, a completely improvised trio featuring Tokyo-based DJ and guitarist Otomo Yoshihide and transgender cabaret icon Justin Vivian Bond.

His journal of his harrowing concert tour of Yugoslavia Suite in ex-Yugoslavia shortly after the fighting ended was published first as a cover story of The Wire, and then included in his book Creative Life: Music, Politics, People, and Machines.

[6] In 2000, Ostertag began a twelve year collaboration called Living Cinema with Quebecois film maker Pierre Hébert.

Her interpretation of Ostertag's work was well received by critics, which led to another collaborative EP, released during the summer of 2012, entitled "The Surgeon General.