Density 21.5

Composed in 1936 for Georges Barrère and his newly acquired platinum flute — platinum having a density of 21.5 g/cm³, giving the work its title — Density 21.5 is among the most frequently performed solo flute works of the twentieth century and a foundational text of the modern extended technique repertoire. Its single uninterrupted movement explores the extremes of the instrument's range, from a brooding low D to stratospheric altissimo, deploying key-clicks, multiphonics, and abrupt dynamic contrasts that were entirely without precedent in flute writing. Varèse revised the work in 1946; the revised version is now standard. In four minutes the piece traverses an emotional journey from ritual solemnity to explosive violence and back, demanding total command of breath, embouchure, and physical projection.