Jacobs was born in Manchester, England, to Jewish parents, Alexander Susman Jacobs and his wife Estelle (née Isaacs). He was educated at Manchester Grammar School and Merton College, Oxford, taking an honours degree in 1946. In World War II he served in India and Burma with the British Army, reaching the rank of lieutenant. In 1953 he married the writer Betty Upton Hughes. They had two sons, Michael Jacobs and Julian Jacobs.
Jacobs was music critic of The Daily Express from 1947 to 1952, The Evening Standard (1956–58), The Sunday Citizen (1959–1965), and The Jewish Chronicle (1963–1975). He reviewed records for Hi-Fi News and Record Review and The Sunday Times and wrote for the arts section of The Financial Times. He was deputy editor of Opera magazine from 1961 to 1971 and served on its editorial board from 1971 until his death.[2][4][5] He considered Edward Dent to have been his greatest influence and encouragement, through both personal contact and his writings.
For The Musical Times, between 1949 and 1996, Jacobs wrote on a wide variety of musical topics, including the New York Philharmonic Orchestra, the Three Choirs Festival, Russian song, The Gypsy Baron, Thespis, the Metropolitan Opera, Leonard Bernstein, Così fan tutte, Trial by Jury, Glyndebourne, Otto Klemperer, and composers from Handel to César Franck to Elgar to Janáček. The writer of his Opera magazine obituary commented that he "was an illuminating, often deliberately argumentative writer and speaker. His reviews were trenchant and outspoken at a time when those qualities were less common than they have since become. He loved to challenge received opinions and liked nothing so much as to disconcert a reader or colleague with an outlandish view", adding that "he was also generous to a fault and an absolute fanatic in the matter of giving the young the wherewithal to improve themselves".
From 1964 to 1979, Jacobs was a lecturer at the Royal Academy of Music, teaching the history of opera. He was head of the music department of Huddersfield Polytechnic (now the University of Huddersfield) 1979–84, where he was appointed to a personal professorship in 1984. Overseas, Jacobs was visiting professor at Temple University (Philadelphia) in 1970 and 1971, at McMaster University (Hamilton, Ontario) in 1975 and 1983, and at the University of Queensland (Brisbane) in 1985.[4] After the Queensland post ended, he retired to Oxford, where he died at the age of 74.