Jascha Heifetz was a Human violinist of the 20th century.
Recognized as a master and considered one of the greatest of his time, Heifetz's technique was one of three hundred individual music styles that were included in Data's programming, and were often occasionally imitated in his performances. (TNG: "The Ensigns of Command", "Sarek")
This character was only mentioned in dialogue.
According to the Star Trek Encyclopedia, 4th ed., vol. 1, p. 332, the birth and death years of Joshua Heifetz were 1901 and 1987, respectively.