2017: Debut releases

Lockhart debuted the i_o moniker in 2017 as part of Mau5trap's We Are Friends, Vol. 7.^[19] He included the electro house song "Warning" as part of the compilation album and was marked as a "powerful" debut as described by a Dancing Astronaut writer.^[20] Online magazine columnists noted that Mau5trap was known to debut emerging artists, including Rezz, Rinzen, No Mana, and Attlas, and so marked Lockhart as an artist to watch;^[19][20] EDM Identity would include him in their 2018 "artists to watch" article.^[21]

In late December, Australian DJ and record producer Tommy Trash collaborated with Lockhart and singer Daisy Guttridge to release "Oxygen". The deep house song was conceptualized from a breakdown idea that Lockhart had sent to Tommy Trash, with the latter recruiting Daisy Guttridge to record vocals.^[22][23] It was well-received by critics, with a writer for Dancing Astronaut noted the song's "atmospheric allure and subdued, deep house vigor" as a departure from what Tommy Trash had been producing for over a decade.^[23]

2018: Extended plays and subsequent releases

On February 20, 2018, Lockhart released his debut extended play Analog//DDoS on Mau5trap. The two-track EP contained the songs "Analog" and "//DDoS" and was well-received by critics.^[24][25] Following the EPs release, Lockhart took over Mau5trap's Twitter account, answering fan questions and "leaking" information, including another EP release in May, an album release by Rezz in late-2018, and several other future Mau5trap releases. The stunt lauded as a PR campaign by EDM Sauce's Erik Mahal, who said it would "go down in history."^[25]

Lockhart released his second extended play, Rootkit, on May 25, 2018.^[26] The 2-track extended play contained the progressive house song "Audio Dust" and the techno song "PassiveX" and was well-received by critics. Karlie Powell of Your EDM described the two songs as a ying to the other's yang, saying that Lockhart presents an "astonishingly diverse style in a 2-track sweep."^[27] In an interview with Billboard, Lockhart explained that he wanted to explore different components of the i_o project, with "Audio Dust" leading as a "more melodic components of the project" while "PassiveX" acts as "an example of where my heart of the i_o project lies: dark warehouses and banging techno."^[28]

Lockhart's third extended play, Scriptkiddi, was released for free on July 17, 2018. The two-track EP consisted of the songs "On Acid" and "The New Wave", both previously featured in DJ mixes before release.^[29][30] Writing for Dancing Astronaut, Robyn Dexter noted that both songs featured on the extended play were "hard-hitting techno heaters, composed of whirlwinds of heavy bass and sultry, computerized vocals".^[29]

2019: "Violence"

Later came a major collaboration with composing and performing the song Violence^[31] along with Grimes. Although it was a side project for her she liked it so much that she included it in her album and made it the first single released from it. By this time she was apparently already aware of his music as she called i_o to do work on the song.^[32] This helped establish his widespread notability and increased promotional exposure through credit in industry publications like Variety where Jem Aswad wrote of the "synth-driven, soft-focus collaboration with DJ i_o".^[33] Positive reviews of the album, the song, and video for it mentioning his credit helped spread his name. Examples of important mainstream media mentions coming from being named a New York Times popular-music 'Critic Pick' by critic Jon Pareles^[34] and the write up mentioning his collaboration in Rolling Stone.^[35]

By the time of his death 'Violence' was his most successful in terms of chart performance. It spent 10 weeks on the Billboard 'Electronic Dance Music' chart, where it peaked at 19th on March 7, 2020.^[36] In other national charts it peaked at 48 on Mexico Ingles Airplay^[37] and 31 on New Zealand Hot Singles.^[38]

2020: Final releases

Finally late in 2020 he was signed to the prestigious Armada Music label^[39] while starting his own imprint named 'Label 444'.^[40] Label 444 and Armada Music were going to be used for releases of different genres. His Armada Music profile page in August 2020 read, "He's joined the Armada family for 2021, with promises of releasing dance smashes on the label. He will also start off the year with his own imprint, Label 444, where his hard underground sound will reside."^[41]

As a featured artist