Stopped pipe (gedackt)
Organ pipe closed at the top; sounds an octave lower than an open one of the same length.
What it means
Gedackt (stopped) is the name for an organ pipe closed at the upper end. Because the air column can then no longer vibrate freely at the end, a stopped pipe sounds an octave lower than an open pipe of the same length. It therefore saves space, especially in low stops.
Musical use
Stopped pipes have a soft, “hollow” sound because only the odd-numbered overtones sound strongly. In the organ they are built as stops such as “Gedackt 8ʼ” or “Bourdon” and often form the basis for calm, gently sounding accompaniment and solo stops. The principle of the stopped pipe is also found in other wind instruments, for example the clarinet, which behaves acoustically much like a stopped cylinder.
The stopped pipe should be distinguished from the open pipe, which vibrates freely, contains all overtones, and sounds brighter, and from reed pipes, which sound with a reed rather than at an edge. It also differs from the flute as a stop through its closed construction and softer sound.
Performance practice
Use stopped stops for calm, soft accompaniment or continuo, where they do not cover solo voices. Mix them with bright stops when you want to brighten the sound, and note that in the low range the tone speaks more slowly.