Hirotaka Izumi (和泉宏隆) was the keyboardist and principal composer of the classic T-Square line-up, and later a solo pianist whose records stayed in print on his own label until the end of his life. He was born in Tokyo on September 28, 1958, and began on the piano at the age of four. He decided on jazz after hearing Bill Evans, and by his teens he was also playing in rock bands. He went through Keio Senior High School, where he played in the jazz circle of the Light Music Society alongside the drummer Akira Jimbo, and then took a law degree at Keio University. The guitarist Yuji Toriyama, a friend from the same school days, would later be the third member of his trio Pyramid.

In 1981 he was a working session keyboardist, appearing on pop albums by Junko Mihara, Mayumi Asaka and, the following year, Naomi Akimoto. In 1982 he joined The Square, the Tokyo fusion band that was later renamed T-Square, and made his recorded debut with them on Kyakusenbi no Yuwaku (CBS/Sony, 1982), where Discogs credits him on piano and as arranger. He stayed for sixteen years, until 1998, and by his own label's count worked on more than thirty of the band's albums. In the studio he covered piano, synthesizers, composition and arrangement, and also horn and string arrangements. In concert he did the announcing himself, in a dry, joking style that fans remembered.

His writing is a large part of why the band's early catalogue still circulates. Japanese Wikipedia credits him with "Travelers", the song that broke the band through, as well as "Omens of Love", "El Mirage" and "Takarajima", the last of which appeared on S.P.O.R.T.S. (1986). The bandleader Masahiro Andoh later said that Izumi's arrival fixed the Square sound, and that before it the band had played with a certain ironic distance and afterward composed in a more serious, planned way. Izumi in turn taught composition to bandmates, among them Toyoyuki Tanaka and Hiroyuki Noritake, who had not written before joining. Wind-band arrangements of "Omens of Love" and "Takarajima" by Toshio Mashima turned the two pieces into a standard school-band repertoire in Japan, and they are still played by junior high and high school ensembles. On Truth (1987), the album whose title track became the theme of Japanese Formula One coverage, Discogs credits him on keyboards, synthesizer and programming.

He made his first record under his own name while still in the band. Amoshe (CBS/Sony, 1988) was recorded in August 1988 with Toriyama on guitar and Akira Jimbo on drums on two tracks, and Izumi composed and arranged eight of its nine pieces. His next leader album, Forgotten Saga (Village Records, 1997), was a solo piano record, and it changed his direction: after it he concentrated on acoustic piano and left T-Square in 1998 with a farewell tour. The saxophonist Masato Honda, who joined the band in 1991 and left it in the late 1990s, is credited alongside him on Megalith (1992), where Izumi wrote four tracks and Honda one, and Izumi later played piano on Honda's solo album Growin' (1998).

After T-Square he built a long solo catalogue. Takarajima (The First Half) (1999) was a piano album of Japanese school songs. In 2002 his own label, Misty Fountain, issued four piano records titled for the hours of the day: 6 to 10 Morning, 14 to 18 Afternoon, 18 to 22 Evening and 22 to 26 Midnight. The solo piano series continued with A Timeless Road (2003), A Promised Movement (2004) and Hirotaka Izumi Covers Love Songs (2005). In 2003 he began playing with Toriyama and Jimbo as the trio O!Kay Boys, which became Pyramid, a guitar, piano and drums unit whose first CD, Pyramid, appeared in 2005 and which Discogs also credits on PYRAMID4 (2019). In the same period Japanese Wikipedia also lists him in an acoustic trio called Voyage with the guitarist Issei Noro of Casiopea and the percussionist Saori Sendo; separately, Discogs credits him on piano and keyboards on Noro's Under the Sky (2001).

From 2007 he led a regular piano trio and recorded four albums by 2009, among them Lights in a Distance (2007), A Square Song Book (2008) and Beyond the River (2008). After the trio changed bassist and drummer in 2010, he formed The Water Colors in 2012 with the bassist Keisuke Torigoe, later replaced by Hiroshi Yoshino, and the drummer Masaharu Ishikawa. The group recorded Shinayakana Kaze (2012) and A Return of Saga (2015), and Discogs credits Izumi on piano on the latter. With the bassist Mitsuru Sutoh, his bandmate from T-Square, he made two duo albums under the name Hiromitsu, 6 on 224 (2014) and Wide & Full (2016). He also worked as a duo with the guitarist Kazuhiko Iwami, as Twilight Express Duo.

He kept returning to the T-Square catalogue. In 2017 the early members formed The Square Reunion, one line-up for the years 1982 to 1985 and another for 1987 to 1990, and he played with both. In 2019 he began Complete Solo Piano Works, a planned five-volume survey of his pieces as solo piano arrangements. In August 2020 he opened a YouTube channel. His last appearance with The Square Reunion was a concert at Blue Note Tokyo on April 4, 2021, and he had been due to appear at the farewell concerts of Masahiro Andoh that summer. He also recorded piano on the saxophonist Ken Ota's Songs from the Heart, which came out in May 2021.

Hirotaka Izumi passed away on April 26, 2021, at the age of 62. His official website announced it on April 28, and the funeral was held for close family only. After many requests from fans, a memorial video with unreleased live footage was premiered free on his YouTube channel on May 2, 2021.

The tributes that followed were substantial. Volumes IV (2022) and V (2023) of Complete Solo Piano Works were finished from earlier live recordings so that the series could be completed as planned. Unforgotten Saga (Misty Fountain, 2022), a tribute album produced by Toriyama and issued under the name Izumi Hirotaka and Friends, brought together many of his former colleagues and included material of his own that had not been released before. T-Square and the Square Reunion members have since played programmes made up entirely of his compositions at Blue Note Tokyo and Billboard Live Osaka, from the first anniversary in 2022 through 2024.

Izumi came to jazz through the piano, and it was hearing Bill Evans that made him want to be a jazz pianist. In The Square and T-Square his role was as much composer and arranger as soloist: the band's most durable pieces are his melodies, and he handled the horn and string arrangements on its records as well as the keyboards. Andoh's remark that his arrival made the band compose more seriously and by design points to the same thing, a writer who gave a fusion group a structure.

After leaving the band he moved toward acoustic piano. The solo and trio records of the 2000s are instrumental and melodic, drawing on his own T-Square pieces, film and television themes, pop songs and Japanese school songs, and Discogs files the 6 to 10 Morning series under Jazz with a Smooth Jazz tag. His work with Pyramid, with Toriyama's guitar and Jimbo's drums, stays closer to fusion.

He is best placed as a fusion and contemporary jazz musician in the tradition of the Japanese studio bands, a composer and arranger more than a bebop improviser. Part of his reach is outside the jazz world altogether, in Japanese pop sessions and in the school wind-band repertoire that carries his tunes, and his reputation rests on the songs.