Born in Moscow and raised in Russia and Israel, Gandelsman comes from a family of professional musicians. His father Yuri played viola for groups including the Israel Philharmonic and Fine Arts Quartet, his mother Janna is a classical pianist, and his sister Natasha is a violinist whose résumé includes the Israel Camerata. Johnny relocated to the United States as a teenager in 1995 to study at Philadelphia's Curtis Institute of Music.
Along with violinist Colin Jacobsen, violist Nicholas Cords, and cellist Eric Jacobsen, Gandelsman formed Brooklyn Rider in 2005. In addition to recording works by celebrated composers like Beethoven and Philip Glass, the quartet is known for performing works by emerging composers, as well as their own original compositions. Their many collaborations outside of the classical realm include recordings by artists spanning Béla Fleck, Suzanne Vega, Kojiro Umezaki, and Gabriel Kahane. Brooklyn Rider made their recording debut via Gandelsman's In a Circle label with 2008's Passport. Around that time, Gandelsman was also recording as a member of Silk Road Ensemble, appearing on albums such as Silk Road Journeys: Beyond the Horizon (2005) and New Impossibilities (2008). The same year Brooklyn Rider released their fourth album, Brooklyn Rider Plays Philip Glass (2011), the quartet also made its Carnegie Hall and Lincoln Center debuts. In 2013, Mercury Classics released The Impostor, a set of banjo compositions by Béla Fleck with the Nashville Symphony and Brooklyn Rider, and a year later, The Brooklyn Rider Almanac comprised commissioned string quartets from jazz, rock, and folk artists such as Bill Frisell, Aoife O'Donovan, Deerhoof's Greg Saunier, and Wilco's Glenn Kotche. While continuing to perform with his string quartet, Gandelsman also recorded with the Knights and played violin on albums such as Aoife O'Donovan's In the Magic Hour, released in early 2016. Later that year, Brooklyn Rider collaborated with opera star Anne Sofie von Otter on classical and pop songs for So Many Things. It featured cellist Michael Nicolas, with Eric Jacobsen having left the group to focus on conducting.
In early 2017, Gandelsman won a Grammy as co-producer of the Best World Music Album, Sing Me Home by Silk Road Ensemble and Yo-Yo Ma. That same year, he also released two albums with Brooklyn Rider and toured with von Otter, Béla Fleck, and Irish fiddler Martin Hayes, in addition to doing his own solo Bach tour. Self-produced and released on In a Circle Records, his solo debut, J.S. Bach: Complete Sonatas Partitas for Violin, debuted at number one on the Billboard Traditional Classical Albums chart in early 2018. ~ Marcy Donelson, Rovi