The Eviola is a designed to be a novel MIDI instrument that can be played with a bow, conceived by Ben Glover and made a reality by J. Dingley. The fingering is based on that of the Nyle Steiner "EVI" electronic wind instrument with four capacitance touch sensors on the main instrument body and four on the bow handle itself, giving a three and a half octave range. Previous electronic bow attempts have met with limited success and this is clearly a technical challenge. We investigated several technologies including optical flow sensing and even time-of-flight range sensing between bow handle and instrument body. The most effective and reliable solution is an adaptation of a rotary position encoder where a wheel with several hundred slots interrupts a beam of infra-red light to produce a pulsed output. By straightening out the slotted wheel we now have a slotted bow. The physical components are a mix of laser cut ply, acrylic and 3D prints with an internal TeensyLC microcontroller reading the sensor data to create the MIDI output. There has never been anything quite like this. The only MIDI bow that ever went into production was short-lived and that provided MIDI data for embellishing the acoustic sound rather than playing MIDI instruments. There has never been a MIDI bow for playing a virtual violin.
The challenge of an electronic bow: It has proved difficult to develop an effective electronic bow and there have been several previous attempts by others. We investigated several technologies including optical flow sensing and a time-of-flight infra-red range sensor between bow handle and instrument body. The most effective and reliable solution is an adaptation of a rotary position encoder where a wheel with several hundred slots interrupts a beam of infra-red light to produce a pulsed output. By opening out this wheel to create a bow with many slots, the speed of movement of the bow can be determined. The infra-red beam runs across a relatively wide slot and so the bow can be moved at a wide variety of angles in all axes through this slot while still sending a reliable signal (pulse stream) to the microcontroller. Fingering: The fingering is based on the system invented by Nyle Steiner for his "EVI" (Electronic Valve Instrument), one of the earliest electronic wind instruments. This packs a wide chromatic range into a small number of buttons. There are implementations for this fingering system available in various modern MIDI breath controllers including the Aodyo Sylphyo. https://aodyo.com/sylphyo-user-guide/#section-fingerings.evi The Eviola is chromatic over three and a half octaves. Based on the EVI fingering system, the three bow buttons on its underside act in a manner similar to the valves of a trumpet while the main instrument body buttons control (half) octaves. In the current configuration the top button on the bow turns vibrato on when you release it. The bow handle is currently fitted with a 16" replaceable wooden laser cut slotted wooden blade. Decision to use breath controller MIDI output as means of expression for the bow: In the demonstration videos, the bow velocity was used to drive a physically modelled violin VST via a MIDI breath pressure data output (not velocity) by the Eviola. Some of the most expressive and realistic violin software, such as SWAM Violin, is designed for use with breath controllers. This is because a continuous controller like MIDI CC #2, breath pressure, is better suited to the control of sustained notes over their duration than keyboard-centric note velocity. The bow is a wonderfully expressive way to play an instrument. The Eviola reconnects this kind of expressive control of software stringed instruments with a physical bow for the first time, by converting the bow movement into MIDI breath pressure data. Open-Source: The design has developed over time and all variations of the laser cutting files, 3D print files and code will be made freely available online as it is likely that some of the users will suggest design variations and improvements. Software upgrades can be loaded by the user: The next innovation concerns practicalities of software and software upgrades. The microcontroller is a TeensyLC board, made in the US. It is compatible with the well-known hobby Arduino ecosystem and downloadable software updates can be easily loaded by the user via the same USB cable that is later used as the USB-MIDI output. MIDI versatility, including wireless: For simplicity, the Eviola can be connected to an iPhone, iPad or PC via USB-MIDI and in those situations is powered from that connected device. A rechargeable battery supply has been incorporated in addition however so that the instrument can also be used wirelessly when a commercially available Bluetooth MIDI transmitter, for example a WIDI-Master device, is plugged into the 5 pin MIDI-out socket provided. Simulation of other stringed instruments: To play an instrument like a violin or a cello takes years of study, but the innovative "Airbow" system developed for the Eviola has the potential to allow other musicians such as keyboardists (or in the case of Ben Glover, a trumpet player) to take advantage of the expressive nature of the bow to play virtual string and other instruments in a more familiar way. It could also be used for all kinds of other sounds of course, and would lend itself well to playing other physically modelled instruments which are driven by breath pressure such as brass and woodwind.