Born in Brookline, Massachusetts, Keszler began playing drums and composing before he was a teenager. He played in hardcore groups as a high-school student and graduated from the New England Conservatory of Music in Boston. Eventually settling in New York City, he began designing performance installations often involving material such as piano wire, motors, and pickups. He started issuing limited CDs of his music through his own R.E.L Records in 2006. His first vinyl release was Livingston, issued by Rare Youth in 2008. He formed the duos Aster (with Ashley Paul) and Red Horse (with Steve Pyne); both issued self-titled debuts in 2009. Keszler's solo CD Tilt appeared the same year.
In 2010, Keszler's solo album Oxtirn was released by ESP-Disk, with Oxtirn Live following on R.E.L in 2011. The year also saw the premier of Keszler's ambitious sound installation, Cold Pin, as well as an album of the same name, issued by Pan. The label also released Catching Net, a 2012 double CD that included the material from Cold Pin as well as a full ensemble performance of the piece. Also issued in 2012 were a live collaboration with Joe McPhee titled Ithaca (8mm Records) and a split LP with Keith Fullerton Whitman (NNA Tapes). Keszler performed with the Iceland Symphony Orchestra at the Transmedial Festival in 2013.
Alps, a collaboration with Oren Ambarchi, was released by Dancing Wayang in 2014. During the same year, Keszler toured the United States with engineer and sound artist Rashad Becker; two years later, they performed together in Japan. Keszler's solo double-LP Last Signs of Speed was issued by Empty Editions in 2016. Keszler appeared on Laurel Halo's acclaimed 2017 full-length, Dust, and performed with her as a duo the following year. He also performed with Oneohtrix Point Never as part of his MYRIAD ensemble and contributed to 2018's Age Of. Keszler's solo album Stadium, his most accessible work to date, was released by Shelter Press that year. The label also issued his 2019 EP, Empire.
Two live recordings from 2018, a set with John Butcher at London's Café Oto and a solo performance of Stadium at the Kitchen in New York, both appeared in 2021. Keszler's studio album Icons was then released by LuckyMe, and his score for the horror-thriller The Scary of Sixty-First appeared digitally at the end of the year. The single "The Vaulting Sky," backed by a Kode9 remix of Icons track "Static Doesn't Exist," surfaced in 2022. ~ Paul Simpson, Rovi