Key Clicks

Edgard Varèse, Density 21.5 (p.1, last line)

During the Twentieth Century, composers expanded the available sounds of the flute to include percussion-like effects. The most common of these is the key-click, pioneered by Edgard Varèse in his famous work for solo flute of 1938, Density 21.5. Key clicks can be performed by themselves; the flutist fingers a specific pitch and slaps a key without blowing (usually notated with an x notehead), or in combination with regular notes. Varèse has chosen the latter for this passage. Note the alternation of key-clicked notes (written with regular note heads with the + notation) with normally-articulated pitches.