How do they do that? Analysing musician’s techniques using load cells
Published On: January 13 2017
In theory, playing a violin should be simple. You just apply pressure with your finger to depress a string onto the neck of the violin, and pass a bow across it to make the string resonate. Easy.
Or not, as many of us who struggled in school violin lessons know all too well. Your best efforts sounds like a reluctant chicken with all claws dug into a blackboard. Nothing like the sweet sound of Nigel Kennedy et all for whom every tune sounds like a lark (ascending). The same applies to almost any stringed instrument, from guitar to banjo, ukulele to cello.
So, how do musicians transform a simple mechanical movement of applying downward force onto a string into something that becomes so sublime? Numerous researchers have tried to pin it down, but analysis using load cells is making progress towards an answer.
Analysing string depression force with load cells
Most of the research done had focused on analysing the posture and movements of players. Tobias Grosshauser and Gerhard Tröster of the WearLab ETH Zurich decided to take a different line of enquiry, namely “The pressure and force applied by the musician while playing the instrument.” (4)
The strings of a violin sit just above the neck of the violin, hovering over the fingerboard. Unlike other instruments, a violin fingerboard is not marked by divisions known as frets, which help the musician place their finger in the right position for a particular note. (That’s why you have a guitar fretboard and a violin fingerboard.) One of the hardest parts of learning the violin is learning where to place your fingers for every note – and then how hard to press down.
So, the researcher’s main task was to build “A force-sensitive-resistor (FSR) based solution for position and force sensing between the contact point of the fingers and the musical instrument.” By placing load cells between the fingerboard and the neck of the violin, the team could measure force without affecting the playing action in any way.
“The position and force sensing embedded into traditional musical instruments … transforms them into tangible interfaces useful for new musical expressions and performance analysis.”
The adapted fingerboard (see images below) features miniature load cells with a force sensing range from 0 to 15 N, and with the top of each sensor touching the neck of the violin. Each miniature cell load consists of a Wheatstone bridge and strain gauges.
New data, new possibilities
While the data beautifully illustrated the various pressures, the more remarkable outcome was that the players stated that they concentrated more on the pressure applied when playing a second time. As the team suggested:
“Learning to separate the pressure from motor control and playing habits leads to a new parameter for musical expression.”
Load cell analysis of historic violins
One of the greatest violin virtuosos of the 19th century was Niccolo Paganini, a composer and performer who created many aspects of modern violin technique. Paganini performed throughout Europe, playing on violins made by master violin makers including Guarneri and Stradivari. Many of these violins still survive and are still played today.
The Italian company Deltatech were commissioned to create a double axial custom bridge in order to detect and analyse the mechanical strain during playing. The finished bridge is a thing of beauty in itself!
Robot violin playing
A group of researchers at the Intelligent Robotics and Mechatronics system LAB in Kyung Hee University (1) developed a robotic finger that enabled a robot to play the violin. Although the research was primarily done to the quest to create “an anthropomorphic robot hand that mimics human hand”, their research (2) threw new light on the differences even minimal changes in force on the string would create.
A 3-axis integrated load cell was developed and mounted on the end of a mechanical finger.
“(The finger) was able to apply an appropriate force on the string when playing the violin. Thus, it is expected that learning the motion of pressing the strings from human becomes possible..”
Robot finger for violin fingering, test for three-axis load cell output test.
Load cells for musical research and projects
If you’re undertaking research into force or strain in musical instruments, and need a bespoke or specialised solution, call us. We can design and manufacture all types of load cells to your specific requirements. All bespoke load cells are made here in our UK manufacturing plant, so we can ship your load cells to you within days, not weeks.
(1) Intelligent Robotics and Mechatronics system LAB, Department of Mechanical engineering, Kyung Hee University Seocheon-dong 1, Giheung-gu, Yongin-si, Gyeonggi-do, Republic of Korea
(2) Development of Robotic Finger Using 3-Axis Load Cell for Violin Playing Robot: Advanced Science and Technology Letters Vol.90 (Mechanical Engineering 2015), pp.22-26 http://dx.doi.org/10.14257/astl.2015.90.06