American violist and teacher Karen Tuttle has died at the age of 90. She famously developed the 'coordination' technique, which balances both the physical and the emotional approach to the instrument.

Born in 1920, she was a successful young violinist before switching to viola in order to study with William Primrose. She became Primrose's assistant at the Curtis Institute, where she taught until 1955. That year, Casals invited her to play chamber music with him at his festival in Prades, Spain.

Tuttle made her debut in New York in 1960, and while living there, played chamber music as a member of the Schneider, Galimir and Gotham quartets. As well as teaching at the Juilliard School and at masterclasses in North America and Europe, she returned to teach at the Curtis Institute from 1986 until her retirement in 2004.

Tuttle's pupils and assistants, including Jeffrey Irvine, Susan Dubois and Kim Kashkashian, continue to teach her techniques at the Karen Tuttle Coordination Workshop, which is held annually in the US.