An organ pipe is one of the tuned resonators that produces the main sound of a pipe organ. Most organ pipes are either long cylindrical metal tubes or elongated wooden boxes of rectangular cross-section.

Organ terminology varies a great deal from period to period, style to style and even from builder to builder. This article gives the most common usages only. For more details, see pipe organ#styles of pipe organ.

There are two types of organ pipes, depending on the way they are driven:

• Flue pipes are driven by whistles or fipples. Most organ pipes are flue pipes. Flue pipes are themselves divided into three broad classes:
  • Flute pipes have the purest tones, and are generally the widest.
  • Diapasons are intermediate in tone, and are the basic sound of the pipe organ.
  • String tone pipes have the richest harmonics, and tend to be the narrowest pipes.
• Reed pipes are driven by a beating reed.

There is another way of dividing pipes into two broad classes:

• Open pipes are open-ended. An open pipe producing middle C is about two feet in length.
• Stopped pipes, also known as closed or gedacht (from the German for covered) are closed at the end opposite the reed or the fipple. A closed pipe is almost exactly half the length of an open pipe sounding the same note.

Stopped pipes are used for two main reasons:

• They tend to be gentler and sweeter in tone. Some builders even go so far as to refer to any stopped flue pipe as a flute.
• Stopped pipes for deep bass notes that would otherwise be difficult to fit into the organ chamber are more easily accomodated, and also cheaper to build. In some organs, the bass notes of an otherwise open rank of pipes are stopped for this reason alone.

See also:

• Pipe organ for more detailed information.
• List of pipe organ stops for a list of some names of different voices of pipes.
• Category:Pipe organ for a list of pipe organ articles.