Walter Howard "Hod" O'Brien (January 19, 1936 – November 20, 2016) was an American jazz pianist. O'Brien was born in Chicago. He attended the Hotchkiss School and then studied at the Oberlin Conservatory and the Manhattan School of Music (1954–1957). He began playing professionally in 1950, and substituted for Randy Weston in 1955. He led his own group in Lenox, Massachusetts during 1956–57, then joined Oscar Pettiford in 1957–58, and J.R. Monterose/Elvin Jones in 1958–59. Between 1960 and 1963, he played with Phil Woods, Freddie Hubbard, Charlie Rouse, and Lee Konitz. In 1964, he enrolled at Columbia University, where he studied mathematics and psychology, achieving his bachelor's degree in 1969; he then took a position in computer programming at New York University during 1969–1974, and