söndag 14 april 2013

Organ failure

Lincoln College organ by Elmar Eye
Lincoln College organ, a photo by Elmar Eye on Flickr.
Music in the chapel at Lincoln College, Oxford used to be supplied by this modest organ by Harrison and Harrison of Durham, but was replaced in 2010 by a new one by William Drake. The old one was a bit undersized and the sound would die from lack of air if too many of the stops were pulled. When I was a student at the college I used to enjoy listening to my friend playing Bach. He was a chemistry student from Shipley and a really good player.

Our own parish church acquired a second-hand organ that was probably originally in a much larger building. It can sound impressive. It can also be a hazard, especially for the choir if it is played too loud when they are trying to sing, which unfortunately it often is. Then they can't compete and end up with sore throats. Worse still, the sound levels can exceed the recommended safety limits.

7 Hz weapon
The organist also has a taste for discords, especially in the bass register. These sound unpleasant. A sound similar to that of a crying baby, or an air raid siren, will arouse feelings of fear and dislike through association and memory, which might be considered a cultural response. It is not just a matter of taste or personal preference, though that comes into the picture. Our feelings of distaste are a biological response. Low frequency discords create infrasound as beat frequencies. Two notes played together in the lower octaves will generate infrasound in the range of 4 Hz to 15 Hz, where people are not even consciously aware of it. The frequency of 7 Hz is notorious. A vehicle designer once told me that it was important to avoid creating structures - railway carriages, for instance - with a resonant frequency of 7 Hz, as it would make passengers feel sick. The same frequency has been mentioned in connection with a US weapons programme, using infrasound at this frequency.

'Acoustic Trauma: Bioeffects of Sound,' by Alex Davies states that the most profound effects at this infrasonic level occur at 7 Hz , which "corresponds with the median alpha-rhythm frequencies of the brain. It is also commonly alleged that this is the resonant frequency of the body's organs and hence organ rupture and death can occur at high-intensity exposures."

In one UK study, it was found that the extreme bass frequencies instilled strange feelings at a concert hall. Effects were "extreme sense of sorrow, coldness, anxiety, and even shivers down the spine." [source; Organ Music Instills Religious Feelings,' by Jonathan Amos, 9/8/2003]

7 Hz infrasound can be produced on an organ by playing at the same time the C below middle C and the C# a semitone above (130.8 and 138.5 Hz). In lower octaves still, for example on the pedal organ, the disturbing infrasound frequency can easily be generated by playing certain chords, in which case the amplitudes will be much higher due to the greater energy in the lower registers with their long pipes. Bottom A and C# are a very unpleasant chord. I wonder if the organist knows this and does it deliberately? I would expect that this piece of information is well known amongst the organ playing fraternity.

An organist at Brompton Oratory used be able to clear the large church in about half a minute by playing the appropriate music. It was more effective than a fire alarm. People made a dash for the exit, probably without realising why. Perhaps this is one reason why I have developed a distaste for my local parish church.

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