‘son filé’ — long, slow bow strokes lasting sixty seconds or more — was regarded as one of the most important practice techniques for developing tone production and bow control. Writing in 1924, Carl Flesch said that son filé “are among the oldest, best-known, most popular and also most appropriate of tone and bow exercises...Their simplicity and usefulness...give them a place of honor in the arsenal of bowing and tonal exercises.” (Carl Flesch, The Art of Violin Playing, pub. Carl Fischer, New