Nicholas Kitchen, founding member and first violinist, said, "When we were faced with the prospect of trying to find a new member, Yeesun [Kim], Mai [Motobuchi] and I were amazed that each of us independently thought of Kristopher Tong as the ideal violinist to join the quartet. We invited him to rehearse with us and felt an immediate and rare chemistry."

Fedkenheuer is leaving to "pursue other opportunities," according to a press release. Born in Binghamton, New York, to parents from Hong Kong and Taiwan, Tong began studying violin in the public elementary school program. He received his bachelor's degree at Indiana University in Bloomington, where he studied with the late Franco Gulli, Yuval Yaron, and Miriam Fried. In 2005 he completed a master's degree at NEC.

Tong has performed with conductors including James Levine, Kurt Masur, Wolfgang Sawallisch, and Charles Dutoit.

The Borromeos made their debut in 1989, and perform over 100 concerts each season. They have appeared in venues including the Concertgebouw in Amsterdam, Opera Bastille in Paris, Wigmore Hall in London, Carnegie Hall's Weill Recital Hall, and Lincoln Center's Alice Tully Hall.