A solar-powered, reprogrammable & hybrid cello

Knurl, a 'cello' with 16 strings, is a shift into exploring the potential of hybrid instruments (acoustic-electronic) to be enhanced through built-in electronic components, as well as the potential for music to be a shared endeavour between performers, and global audiences members and its networks. Knurl is solar-powered, reprogrammable (performers and audiences can interact and manipulate) & hybrid cello. Its 4 modes of performance (Synthesis, Detection, Programming & Analogue mode) are installed in a microcontroller in a self-contained electronic circuit, (all the electronic devices are attached to it, including speakers, microphone, microcontroller, solar panels and sensors). 


In November 2018, the project to build an electric cello was born through the initiative of me and more 3 classmates (Sonology(2), and art-science (2)) in the Royal Conservatory of the Netherlands. Our original intention was just to make our own electric cellos in order to play music together. My colleagues sketched a thin electric cello, with 4 strings and guitar pickup. On my first version, I aim a new cello with 12 strings, made simply of wood with a microcontroller and sensors. In the process of development, it evolved into its current format of recycled RPET plastic, with 16 strings, hybrid (acoustic & electric), rechargeable and reprogrammable.

           The name ‘Knurl’ (metal slippery surfaces with its tiny grippy tips) came up from the use and the apprehension of the human body movement, using friction on the knees to change the position of the instrument on the performer’s body. Likewise, as the crickets, we have to find a grip in our legs in a knurling surface (Kenny patterns from the angle and/or grossed lines of in a smooth metal surface ) to produce 'energy'.

           It can charge itself by a photovoltaic solar system, being one of the pioneers electric instruments sustainably designed with energy ​free and self-contained circuits35. A ​solar pedal separates its acoustic functions of absorption and reflection, storing the electronics and being portable to adapt the solar panels to the light sources. By a switch, you can change the functions of the solar panels, treating it as an analogue sensor for music parameters.

        The design reinvents conventional issues of a cello into advantages while offering a new array of possibilities that radically expanding the instrument's range and sonic palette. Fourth buttons define specific triggers from a selective mode of performance (synthesis, programming, analogue & detection mode). It's possible to play different modes at the same time by changing the settings on a capacitive switch button, made on the Bela trill Craft36. Those buttons can select and trigger synths or code functions that process the sound of both the cello and, potentially, the audience. This tool is geared for live electronic performances, in which the performer and audience can interact as the music unfolds in real-time. An oled screen shows to the performer the code that has been reprogrammed.

         On Knurl, to create chords, different multiphonics or combinations of harmonics are possible in a melodic instrument. The tuning system can be adjustable to your aesthetic purposes (without damaging the instrument). Inclusion is certainly also a matter. The bridge is designed depending on the performer's height. The rotational angle of the instrument, which impacts the sound, is readily manipulated by the pressure of the player's knees and feet. ​The principle of the traditional scordatura ( tuning system) of the cello is the same: The strings can be tuned by intervals of fifths, such a conventional cello:

Although I consider Knurl as a non-tuning instrument, where the search for harmonic, color and gestalt connections become part of an intuitive discovery of cognitive connections, as I would consider the reaction instruments part of this scientific identity.
    Knurl has 8 capacitive buttons. Using digital functions, I transformed them in 2 Analogue buttons (range button), 4 digital buttons (on & off) and 2 switch buttons (management buttons, red (stop all) and mode (switch to one of the 4 modes of performances)).
















Fig.8 : Knurl buttons

In its sound system, 4 speakers of 4 ohm are connected into the bela Board ( Since bela only handles 8ohm, I connected 2 speakers in series with the others, having then 8 ohm of each channel. Therefore, Knurl is stereo with the possibility to implement a 4 channel sound system if connected to an amplifier class D.



















Fig. 9: sound system of Knurl

The speakers in the bridge are disposed of in an angle directing hifi & lofi reflections in a stage/concert hall environment. The speakers at the bottom part improve lofi reflections, by its angle adjusted towards the floor or ceiling.


This project was realized during my studies at the Sonology Institute of the Royal Conservatoire of the Hague, my experience at Revspace hackerspace, the workshop of queen's mary university (Absurd music instruments), the meet ups from the Netherlands coding Live. A special thanks to the help and support of those artists:


collaboration between Mercury & Knurl


sound engerineering   | collaboration on DINA

Knurl platform

Programming skills, workshop

Editorial about Archive

collaboration mapping my mapping

Editorial team