Resonance decay
Sound remaining after a note ends.
What it means
Resonance decay (German Nachklang) designates the sound still audible after the excitation has stopped. Two processes are to be distinguished here: the decay of the instrument itself — a plucked string, a bell, a cymbal continue to sound until their vibration dies away — and the reverberation of the room, which arises from countless reflections off walls and ceiling.
Musical use
For practice, the room is the more important factor. Its reverberation time co-decides how a performance comes across: a reverberant room connects the notes and forgives little clarity — fast passages blur, chord changes overlap, and a too-quick tempo makes the music unintelligible. A dry room creates clarity but demands more sustaining power from the tone and more care in the transitions, because nothing gets connected. Churches and large halls differ considerably in this from rehearsal rooms, and the same piece wants to be played differently in the two places.
Instruments, too, behave differently. On the piano, the resonance decay can be controlled by the pedal — it lifts the dampers and at the same time lets related strings vibrate along, which makes the sound fuller. On organ and percussion, the decay is part of the shaping; for winds and strings it arises solely from the room.
How long and how a note decays depends on the instrument and the room. Bells, cymbals, gongs, and the piano with the damper raised have a long decay, woodwind instruments by contrast hardly one of their own. In the room, the reverberation lengthens the sound; in large churches it can last several seconds. Composers have deliberately used resonance decay as a means of expression, for instance in pieces that work with rests and resonance.
Performance practice
Try out in the performance space how long the sound stands, and orient tempo and articulation accordingly: in reverberant rooms, separate more distinctly, take it somewhat calmer, use the pedal more sparingly. Listen after the last note instead of cutting off immediately — the decay belongs to the piece. And factor the room into your pedal use: what sounds clear in the practice room can blur in the church.