Jay Yoo is a guitarist, composer and arranger who is originally from South Korea and is now based and active in Toronto. His own biography, repeated by the Rex Hotel Jazz and Blues Club and by Bellotto Music, describes him as a versatile player who works across jazz, funk, rock, R&B and musical theatre. No birth date, no Korean city of origin, no Korean-script spelling of his name and no account of when he moved to Canada is published anywhere, so none is given here; Jay Yoo is the name on his records.

He holds a Bachelor of Music in Jazz Performance from the University of Toronto, where he received the Noreen and Phil Nimmons Entrance Scholarship, and his biography names Geoff Young, Mike Murley and David Occhipinti among his teachers. In August 2019 he attended the Banff International Workshop in Jazz and Creative Music, where, according to the same biography, he studied with Matana Roberts, Linda Oh, Vijay Iyer and Tyshawn Sorey. He then returned to the University of Toronto for a Master of Music in Jazz Performance as a student of the guitarist Ted Quinlan, and gave his master's recital at Heliconian Hall in Toronto on April 5, 2024. The printed program does not say whether the degree has since been completed.

The groups named in his biographies are the fusion bands Super Breakfast and the Dennis Kwok Quartet (the Rex calls it the Dennis Kwok Electric Quartet), the award-winning band Snaggle, his own Jay Yoo Group, and the groups of the Toronto vocalist Jenna Marie Pinard, Jenna Marie Sings R&B and the Jenna Marie Jazz Group. The Rex also lists him in Haneum, a traditional Korean fusion band run by the Korean Traditional Music Association of Canada.

His first record is Here, Now, a duo album of guitar and voice with Pinard, released on November 3, 2019. It holds eight tracks, among them the standards "A Nightingale Sang in Berkeley Square", "Two Sleepy People" and "You Don't Know What Love Is", a "Green Eyes" with a short introduction, and the titles "Mermaid Island", "Providence" and "Polaroid". The Bandcamp credits name Pinard on vocals, Yoo on guitar, Tom Upjohn for mixing and mastering, Gowan Kim for the album design and Kristian Fourier for the photograph. A video shows the pair playing "You Don't Know What Love Is" at Café Résonance in Montreal, and his biography says the album was presented in Toronto and Montreal.

Dual Unity, a duo album with the pianist Mark Kazakevich, followed on May 13, 2022. His biography says he recorded it during the pandemic. It has nine tracks, six of them written by the pair, with "Insensatez" by Antonio Carlos Jobim, "Quero Não" (credited by the reviewer to Tania Maria) and "Voyage" by Kenny Barron among the covers. WholeNote reviewed it on May 20, 2022 and called the pairing a natural one, and Jazz Weekly's George W. Harris reviewed it that August; the Rex also credits it with a place in a Vancouver Sun list of albums by guitarists to hear.

The April 2024 recital shows the range of his writing and arranging. Its program lists his own pieces "The Odd Journey of Apollo 12", "G.", "Cosmic Latte" and "Porpoise", his arrangement of "Gone with the Wind", Kenny Kirkwood's "We're Not Home Right Now", Toninho Horta's "Aquelas Coisas Todas", and three Korean folk songs arranged by him, "Sangju Arirang", "Sin-a-wae-gi" and "E-uh-do-sana". His band was Matt Savard on bass, Michaël Filion on drums, Walter Chan on saxophones, Lily Kim on percussion and Sangah Lee on voice.

Two months later, on June 14, 2024, he released Cosmic Latte, a five-track EP billed to Jay Yoo with Mads Tornemark, Franciszek Wicke and Jan Kusz on the cover. Four of its titles are in the recital program: "The Odd Journey of Apollo 12", "Cosmic Latte", "We're Not Home Right Now" and "G.", with "Distant" as the fifth. On June 16 and 17, 2024 he led the Jay Yoo Quartet at the Rex, with the drummer Anders Morgensen, listed as from Denmark, and the saxophonist Allison Au (listed as to be announced).

He is also the guitarist on two releases by the Toronto bassist Robert Lee, the live EP Live at the Small World Centre (2023) and the album Forbidden West (2025), the latter built on Korean folk stories and the gayageum.

His Korean connection runs through his origins, the Haneum band and his folk-song arrangements. The sources found describe his working life as a Toronto one, and none documents a career in the Korean jazz scene.

He does not name his influences in any source found, so this section sticks to what reviewers and programs show. Jazz Weekly hears a clean, linear guitar that turns warm on "More To It" and impressionistic on "Dream", with Kazakevich closer to Keith Jarrett in fluidity. WholeNote describes a set largely inspired by contemporary and Brazilian jazz, and says Yoo's interjections blend into walking basslines that both punctuate and support.

Brazilian music recurs: Jobim's "Insensatez" on Dual Unity and a Toninho Horta piece in his recital. The standards on Here, Now and "Gone with the Wind" at the recital place him in mainstream jazz, while his own bio's references to fusion bands and to Korean folk melodies on guitar mark the edges of that. Funk, rock, R&B and musical theatre are listed as parts of his working life; the records described here are jazz records.