Jascha Heifetz (1901–1987) was rumored to practice three hours a day, not twelve. How, then, did he achieve a vibrato smoother than silk, shifts without a trace of glissando, and a bow arm that produced a tone of unparalleled purity?
: Single-note scales in three and four octaves, as well as whole-tone and chromatic scales. The Heifetz Scale Book For Violin Pdf