Iwaki was born in
Tokyo in 1932. Shortly after he entered an
elementary school, he moved to
Kyoto due to his father's transferral. He came to play the
xylophone at nine years old. He moved back to Tokyo when he advanced to the fifth grade. In May 1945, suffering from an
air raid, he evacuated to
Kanazawa, where his relatives lived. After the end of
World War II, he moved to the mountainous area of
Gifu for his father's work. In 1947, he was admitted to Gakushuin Boy's Junior High School, graduating in 1951. He had applied for admission to the Department of German Literature of
University of Tokyo, but he gave up on account of a high fever he ran on the eve of the examination. Eventually he went to the Percussion Department, Faculty of Music,
Tokyo University of the Arts. However, he dropped out later. In that era, discrimination existed depending on one's specialty within the faculty, and above all, the Percussion Department was ranked among the lowest group in the faculty. He made his conducting debut with the
NHK Symphony Orchestra in 1956, and was later honored as permanent conductor of that orchestra. In 1977, he became the first Japanese to conduct the
Vienna Philharmonic, as a substitute for
Bernard Haitink, who had taken ill. He first conducted the
Melbourne Symphony Orchestra (MSO) on a 1973 Australian tour, and was chief conductor of the MSO for a record term of 23 years (1974–97), during which time he took the orchestra on two tours of Japan. In 1990 he was appointed the orchestra's conductor laureate, while remaining chief conductor until his retirement in 1997. He remained the conductor laureate after retirement. He made efforts to found the
Orchestra Ensemble Kanazawa and was appointed as the first music director, where he established the composer-in-residence system and tried hard to perform their commissioned works first in the world. He conducted all the
symphonies of
Ludwig van Beethoven in one concert at
Tokyo Bunka Kaikan, from the afternoon of 31 December 2004 to the morning of 1 January 2005. In the following year, he performed the same program again from memory at
Tokyo Metropolitan Art Space on 31 December 2005. On 13 June 2006, he died of
heart failure in Tokyo, Japan. ==Honours==