Flutists are lucky to have solo works written by some of the leading 20th-century composers including Edgard Varèse, born on this day in 1883. The composer’s affinity for electronic sounds is reflected in the sharp dynamic changes of Density 21.5 that make it exciting to practice and perform. The extremes of range throughout the piece push the possibilities of the instrument and were likely meant to show off the capabilities of Georges Barrère’s newly-minted platinum flute, to which the composition is dedicated. We who play simpler, silver flutes still find joy in exploring the possibilities of our instruments by performing this work.