Home       Research      Publications      Teaching
rdmg1 at dmu.ac.uk

The O-Bow
A bow sensor musical instrument
(Optical bow a.k.a L-Bow, Light bow. Pick your preferred pun..)

newslatest prototype  first prototype  |  background 

March 2013

Following a demonstration and paper at the Tangible Embedded Interaction conference in Barcelona New Scientist magazine ran a feature on the O-Bow. In response to this a short new video (added below) was prepared which triggered more magazine articles and then a story in the paper edition of The Daily Mail. Not all the information published is accurate but the overall response  was very positive. Here are links to some of the articles:

New Scientist
The Daily Mail
Arts Journal
Tech Gadget

February 2013


Short violin run. I'm using a short bow which is easier to handle. Longer bows are good for long sustains.

See below for high quality wav audio.

obowKeysMac_shrunk.jpg O-bow2_closeup_shrunk.jpg

The fifth prototype is finished.

New feature summary:

- robust tracking from low to high speeds for variety of surfaces including standard bow hair types.
- bow contact parameter, enables ringing string sound when bow is removed while bowing.
- all communication is using the USB-MIDI protocol providing immediate connection to music software.
- cylindrical casing design for flexible configuration and orientation, for example using standard mic holder.
- contact saddle manufactured from optimized CAD design, for bow engagement and tracking.
- software moved to the Native Instruments Kontakt platform. The script language is strong enough to implement all the O-Bow features. This allows the O-Bow to operate as a virtual instrument in a wide variety of music software.
- manipulations are possible on the control data directly in a sequencer.
- speed to gain warping for a variety of playing feel.
- new violin sample recordings, including ringing. Many thanks to violinist Motje Wolf. The sample sets are incomplete and not fully produced. Complete sample sets will be incorporated later.

Audio examples:

The following clips were produced by recording gestures in a sequencer then synthesizing, some with pitch/tempo edits.

violin run 
violin, low  | (wet) bowing, legato, vibrato, staccato, ringing
violin, high  | (wet)
opening triple bounce is from natural bow bounce
cello  | (wet)

cello edited  (wet)
in the sequencer the pitch is transposed up and the tempo increased. Note that the vibrato rate stays the same : this is impossible using audio time stretch.
cello warped  (wet)
the bow speed is warped so that lower speeds are raised, creating a flatter performance.

Sequencer screen shot:

An example of how control parameters can be edited directly.

July 2011

The following photo shows a new prototype being used with Eigenlabs Eigenharp Alpha. This allows precision bowing to be combined with the sensitive and highly controllable keys of the Eigenharp, in a natural cello configuration.

A closeup of the O-Bow prototype -

November 2010

Engadget magazine published an article about this here.

February 2010

The first prototype. Synthesis implemented using Max/MSP and a single violin sample.

A youtube video is shown below. The original video (for better quality) is available here.

This prototype works with a wide variety of bowing material, including real bows and wood. The natural grain of wood provides useful passive haptic feedback, whereas the spring of the real bow helps with bouncing off the contact. The reduced weight of a simple wooden rod can be an advantage.


The O-Bow is an electronic musical instrument consisting a bow sensor and synthesis software. An optical flow sensor is used to measure the bow speed and horizontal angle with high resolution. A variety of bow types can be tracked, including violin bows and wooden sticks.

Development of the O-Bow was prompted by the obvious need for something like a windcontroller but for string instruments.  Increasing amounts of orchestral music in tv and film is produced using sophistocated sample based instruments played using keyboards. String sounds are some of the hardest to generate convincingly because of the variety of possible expression. The initial  aim for the O-Bow  was to find a way to add more expression in this setting.
It is also expected to be popular for live performance and in education. Because it is electronic there are no restrictions on what kind of bowed sound might be produced.

It is not intended as a replacement for a real violin!

A real string instrument requires careful control and coordination of bow velocity, down-force, bow position, finger position and vibrato, including time evolution, which can take many years to master. The O-Bow requires only the control of velocity and can be made much more forgiving to play, while retaining considerable expressive potential. Pitch can be controlled using a conventional keyboard or other controllers such as ribbon controllers. Additionally, bow angle is found to be useful for controlling vibrato intensity, freeing the non-bowing hand for key work. Down force sensing may be added in future designs, but is not currently seen as a priority.

From a broad perspective, bowing is a very natural, ancient mode of expression. It deserves to be integrated better into the modern world of electronic sound. This includes the creation of instruments that go beyond direct emulation of bowed instruments.

The method of synthesis adopted here is based around the modification and playback of recorded string samples. In practice this approach works better than expected, partly because the variety of bowing produces a wide variety of gain profiles, and variation in resynthesis, particularly at the critical onset stage. Of course it is difficult to capture every detail of behaviour in this way. Physical models offer the potential for much more realistic and rich behaviour, but they have some disadvantages: It is hard to make a physical model fit well to a given instrument. Even when this is achieved successfully, the result may be as difficult or more difficult to play than the original and require many sensor inputs, particuarly true in the case of the string instruments. So while physical models are expected to play an important role in the future, they are not a focus initially in this project.

 The O-Bow is the subject of granted and pending patent applications.

rdmg [@] dmu.ac.uk