Gregory W. Brown has always been a tinkerer with a love for gadgets. In addition to coding (primarily in ChucK), he has built one of the few existing electromagnetically prepared pianos.

Basic description: analog audio signal is amplified and sent to electromagnets placed in close proximity to piano strings. This amplified signal causes a variable electromagnetic field which causes the strings to vibrate, in turn creating sound. I built the equipment necessary for this preparation during 2010–11 based on research available on Steven Backer’s page at Stanford, though I have made some modifications to better suit my aims. Special thanks to Per Bloland who kindly pointed me in the right direction.

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This instrument was featured as part of two radio spots on WRSI and NEPR in March 2012.

Playing the Instrument

The instrument can be played using analog signal. Any signal (converted to analog at an appropriate level) can work. I have experimented with Sine waves, audio signal (sung, spoken, etc.), and feedback loops.

Recording the instrument is surprisingly difficult. Here is an extended session of improvisation using the iPad feedback controller (see below).


The device responds particularly well to feedback. I’ve designed an iPad interface to dynamically manipulate feedback loops and generate a wide variety of colors and sounds. It can also be played (though less flexibly) through analog boards.

The Cyclopean Harp

I have an installation which algorithmically creates feedback loops in non-synchronous cycles. The variety of sounds that result is surprisingly varied.

The Cyclopean Harp was installed on October 18, 2013, at the Phillips Exeter Academy Library in Exeter, NH. See this page for details.

The Lily in a Crystal (after Herrick)

The Lily in a Crystal (after Herrick) is my first work for electromagnetically prepared piano. All of the sounds are generated either by typical means, harmonics (reaching inside the piano), or by electromagnetically actuating the strings (see above). There are no loudspeakers involved.

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