New string theory explains guitarists’ sounds

A University of Oxford scientist has developed a new string theory in which he describes how the techniques employed by lead guitarists result in their distinctive sound. Methods such as string bends, vibrato and whammy bars – a control lever to change the tension of strings – are used to change the pitch of a note, and Dr David Robert Grimes has derived equations to explain how. “Very good guitarists will manipulate the strings to make the instrument sing,” said Grimes. “On a piano, you’ve got the 12 chromatic notes in a scale. On a guitar you can bend the strings to get the notes in between. I wanted to understand what it was about these guitar techniques that allows you to manipulate the pitch. Grimes – a postdoctoral researchers in the Department of Oncology – found that the properties of the strings had a big effect on change in pitch, in particular the Young’s modulus, a measure of how much the string stretches under force, and how thick they were. The scientist – more used to modelling oxygen distribution in radiotherapy – also worked out how easy hammer-ons and pull-offs are, depending on the height of the guitar strings above the finger board. The equations were experimentally confirmed by measuring the frequency of the sound produced for strings bent through different angles on a guitar. “I took one of my oldest guitars down to the engineering lab at Dublin City University to one of the people I knew there and explained I wanted to strip it down to do this experiment,” Grimes said. “We had to accurately bend the strings to different extents and measure the frequency produced. “He was a musician too and looked at me with abject horror. But we both knew it needed to be done – we put some nails into my guitar for science.” Although the physics of vibrating strings and string instruments has long been understood, this is the first time someone has worked out how bending the string can change the pitch. No-one had previously worked out how this depends on the tension of strings, the force applied and the angle through which it is bent either. “It turns out its actually reasonably straight forward. It’s an experiment a decent physics undergraduate could do, and a cool way of studying some basic physics principles,” Grimes said. String theory – the physics of string-bending and other electric guitar techniques Dr Grimes explains his work in a video on this story http://www.youtube.com/watch?v=SNj7s_tTOs0