Research reveals how pipe organs create an auto-tune effect

By Stephen Beech

Pipe organs create an "auto-tune" effect, according to a new study.

The giant instruments, with a strong timber base and towering metal pipes, create "sympathetic resonance" in concert halls and churches, say scientists.

Even when not in use, researchers found that a pipe organ affects the acoustical environment around it.

Ashley Snow, of the University of Washington in the US, set out to understand what effects the world’s largest class of musical instrument has on the acoustics of concert halls that house them.

Snow said: “The question is how much the pipe organ contributes to an acoustic environment - and the bigger question is, what portion of music is the acoustic environment, and vice versa?”

The research team hypothesized that the pipe organ creates an auto-tune effect since its pipes sympathetically resonate to the same frequencies they are tuned to.

The effect may enhance the overall musical sound of ensembles that play in concert halls with organs.

A "sine-sweep" - a resonance test in which a sine-wave-shaped signal is used to excite a system - was played through loudspeakers facing the organ pipes and measuring the response with a microphone at different positions.

Data was gathered by placing microphones inside and around the organ pipes during a musical performance and a church service.

Snow said: “I was way up in the ranks dangling a probe microphone into the pipes, trying my hardest not to make a sound or fall."

The researcher verified experimentally that sympathetic resonance does occur in organ pipes during musical performances, speeches, and noises at frequencies that align with musical notes, and that the overall amplitude increases when the signal matches the resonance of one or more pipes.

Investigations are still ongoing into the significance of these effects on the overall quality of musical performance to listeners in the audience.

Snow hopes to expand the research by comparing room acoustics between rooms with and without the presence of an organ, along with categorizing and mathematically modeling the tuning system of different world instruments.

Snow added: “What about the sympathy of a marimba, cymbal, or piano strings? Or the mode-locking of horns in a band?

"Would it sound the same if these things were separated from each other? For better or for worse?

"I want people to think about that.”

The findings were presented at a virtual meeting of the Acoustical Society of America.