blocked keys

A piano technique in which the performer silently depresses certain keys with one hand (or fingers) without sounding them, leaving the dampers raised. When the other hand then plays in the same register, the sustained vibrations from the silently held strings create resonance and overtone enrichment of the sounding notes. This is the defining technique of Ligeti's Étude No. 3: Touches bloquées. The \"blocking\" hand holds certain keys while the other hand plays rapid, repeating patterns; the blocked keys act as harmonic filters, modifying the timbre of the sounded notes and creating eerie quasi-harmonic resonances. Related techniques appear elsewhere in the Études in a looser form.

In Touches bloquées, identify which hand is \"blocking\" (silently holding) and which is playing — this varies in the score. The blocking hand must apply sufficient weight to raise the dampers without making any audible sound. The effect is most striking with a well-regulated concert grand; on a smaller piano or a digital instrument, it is less vivid. Begin by learning the playing hand's pattern completely alone; then add the blocking hand very slowly, listening for the timbral modification. The tempo must be accurate: if the blocking hand releases or shifts at the wrong moment, the effect collapses.