This is a quick demonstration of Dylan Menzies’ O-Bow 1, an optical bow prototype. The bow speed controls gain, & bow angle controls vibrato.
Note how expressive the result is, despite the fact that the demo uses a single sample for synthesis.
Here’s what Menzies has to say about the optical bow controller:
The O-Bow is a bow controller consisting of an optical flow sensor mounted to measure the bow speed and horizontal angle with high resolution. The bow can be anything with a grained surface, such as a wooden stick.
Development of the O-Bow was prompted by the lack of robust, and inexpensive bow controllers. Synthesized string instruments frequently appear in recordings, yet the quality of articulation is very limited for such expressive instruments. Bowing is a fairly easy skill to aquire, whereas fingering and vibrato are very difficult. Combining the keyboard with bow allows a musician previously unskilled with string instruments to quickly produce much better articulation than using a keyboard alone. Controlling vibrato with bow angle or key pressure avoids the need to control vibrato directly.
From a less utilitarian viewpoint, bowing is a very natural and expressive mode of control. It deserves to be integrated better into the modern world of electronic sound, including that which is more removed from authentic strings.
So far the O-Bow has been used with a simple one-sample synthesiser as shown in the following video. More sophistocated synthesis is being developed, including physical modelling. A related patent application has been filed.