Forty-four bells that are never rung

Forty-four bells hang in the tower of Grace Cathedral in San Francisco, up on Nob Hill. The smallest are the size of a football, the largest stands taller than a person at over six feet. Nobody strikes them. The whole installation is about what they are doing while they stay silent.

Sound artist Bill Fontana has gaffer-taped vibration sensors to a few of them — accelerometers that look like silver thimbles. What follows is technically dull and therefore convincing: the sensor runs by cable to an amplifier built to handle vibration signals, and that signal is turned into audible sound.

What do they catch? Wind. Construction. And San Francisco’s cable cars — municipal transport, which to a bell is simply another kind of tremor. The bell stops being an instrument here and becomes a microphone aimed at the whole hill.

Fontana’s idea is larger than the tower: everything in the physical world has a resonant frequency, so any structure is potentially a listening device. It sounds like a metaphor until you notice he has spent fifty years on it and produces the evidence each time.

Before the bells there were the sounds of melting glaciers in Austria, the vibrations of the Millennium Bridge in London, and ancient sequoias. The cathedral piece is part of an artist-in-residence programme, and it runs through late September.

The interesting part is not the equipment but the assumption it inverts. We go to concert halls to hear what someone is playing. Fontana suggests going to hear what has been sounding all along, only too quietly for anyone to have noticed.