Organ pipes are primarily measured by their length, as this crucial dimension directly determines the fundamental pitch or note they produce. This measurement is fundamental to how an organ's sound is designed and understood.
The Direct Relationship Between Length and Pitch
The core principle behind organ pipe measurement is that the pitch of any pipe is proportional to its length. This means a longer pipe will produce a lower pitch, while a shorter pipe will produce a higher pitch. This inverse relationship allows organ builders and musicians to predict and control the musical notes produced by each pipe.
For instance, pipes are often referred to by their "foot length," which indicates their approximate length and, by extension, their sounding octave. This system provides a standardized way to categorize and understand the range of notes an organ can produce.
Practical Examples of Pipe Length and Pitch
The following table illustrates the direct correlation between an organ pipe's length and its resulting pitch, as commonly understood in organ building:
| Pipe Length (Imperial) | Pipe Length (Metric) | Corresponding Pitch / Effect |
|---|---|---|
| 8 feet | 2.4 metres | Normal keyboard pitch |
| 16 feet | 5 metres | Sounds its sub-octave (one octave lower than normal) |
| 4 feet | 1 metre | Sounds its octave (one octave higher than normal) |
This system allows organists and builders to quickly grasp the pitch characteristics of different stops (sets of pipes) within an organ. For example, an "8-foot stop" means that the longest pipe in that stop (typically the lowest C) is approximately 8 feet long, producing notes at the standard keyboard pitch.
While other factors such as diameter, material, and voicing techniques significantly influence the pipe's timbre and harmonic content, the length remains the primary measurement for determining its fundamental pitch.
