Stringed Musical Robot

Research project on the development of new tools for musical expression

<Zibalo>

a hammered zither playing robot

dr.Godfried-Willem RAES

2009-2025

<Zibalon>

In our quite large collection of musical instruments at Logos Foundation, we had since very long a bunch of different Zithers of different kinds: German made ones with some 48 steel strings, a Han-Koto as well as a few zithers stemming from 19th century musical automatons. The latter I digged up from the cellar of my grandmothers (1899-1996) house. They were completely rusted... For many years we had thoughts about finding a way to turn at least one of these zithers into a musical robot. The problems, as soon as we started experimenting and designing it on the drawing table seemed very unsurmountable. The main reason being the too close spacing of the strings. No matter what kind of plucking mechanism we imagined, it either took too much physical space (using bidirectional solenoids) or it would be way too slow and monophonic (using a sledge mechanism with a single plectrum) to allow automation of all of them. So the idea was dropped for many years.

In 2013 we were asked by Osama Abdulrassol to consider the automation of an arabic Qanun. The same problems we had analysed already reappearing and some new ones in top: the Qanun uses microtonal pitchchanges using a mechanically pretty simple system (mandalar) , but again due to size/force constraints, very difficult to automate well. Although in may 2013 we decided to have a throw at it, and started making a first prototype for a plucking mechanism. The perspective being to also make the zither itself rather than trying to automate an existing instrument. For the first time in our carreer as a robot designer, we decided to construct the automation mechanism prior to and fully independently of the actual sounding instrument. This entails that we designed the actual instrument only after the mechanism for the plucking was fully up and running. Thus, first a prototype plucker was made using a solenoid assembly from Syndyne. Detailed information about this design and its final failures can be found on the legacy <Zi> webpage. The mechanism never had enough force to really pluck the strings. Hence we recycled the mechanism and thus the <Tinti> robot was eventually born...

A second attempt to build a plucking mechanism was made, making use of bidirectional solenoids with permanent magnets. These solenoids are stable in either of their end positions and they only require a pulse of changing polarity to make them change position. As this type of solenoid could not be obtained with an anti-rotation shaft, we decided to design round plectra with a 2 mm central hole for plucking the strings. However, once eastmore, it was a complete failure. The solenoids only develop some force in either one of their end-positions, whereas for or a decent plucking mechanism, most force is required in the middle of the trajectory. Experiments we carried out prove that presumably the best pluckler mechanisms can be made using stepping motors. As a consequence, spacing between the strings has to be quite large, say at least some 50 mm.

Third time, good time as a Dutch proverb claims, we forsake the idea of plucking and turned back to an old German made zither in mint condition. Instead of plucking, now we used a hammering mechanism. So, organologically speaking, we turned the project into some kind of cymbalon, a hammered citer after all. The hammering mechanism was derived from the design of the 'poltergeist' we designed for our <Ubu> robot. It uses small solenoids to load a spring and on release of the power, the anchor bounces back against the string. Velocity control is very well possible by varying the pulse durations. Very short pulses and quite high voltages ( 48 V) are mandatory here.

 

Only when integrated in the context of our M&M robot orchestra with its wealth of varied sensor systems allowing full interactivity with gesture and audio, this automate will become a true robot. That's after all were its destination is to be sought.

Midi Mapping and implementation:

This is the ambitus for the instrument when using the original steel strings. This also is the ambitus as implemented in MIDI.

Midi channel: fixed to 4 (counting 0-15).


Note Off: Not at all required.

Note On: Implemented for notes in the range. Velo-byte is used for the striking force. The lights are also mapped on notes, but make use of a range outside the normal range of the zither.They are mapped on notes 120,121.

Channel aftertouch: can be used to let notes repeat automatically. The parameter value sets the repeat frequency. The command can be sent even prior to note-on commands. The value sent will be preserved until reset with a new channel aftertouck command

Controller 30: Can be used to set the repetition rate of the notes.

Controller 66: Robot on/off switch. Sending a power off command (Ctrl 66 set to 0) will cause a reset of all controllers to their default start up value. Also settings for note repetition will be reset.

Controller 123: all notes off. Stops note repetitions.

 

Technical specifications:

Design and construction: dr.Godfried-Willem Raes

Collaborators on the construction of this robot:

Music composed for <Zibalo>:

 

 

Back to composers guide to the M&M robot orchestra.

 Back to Main Logos page:index.html To Godfried-Willem Raes personal home page... To Instrument catalogue Go to Godfried-Willem Raes' homepage

 

Construction & Research Diary: