Designing Mechatronic Musical Instruments: The Guitar

Abstract

Since the earliest times, humans have sought the ability to produce rhythms and tones using devices external to the human body. As technology developed, so too did the desire for this sound production to become automated. Initially peaking around the Industrial Revolution, traditional automated musical production devices went into a steep decline with the arrival of the phonograph. However, factors such as the ubiquitous acceptance of the microcontroller led to a resurgent interest in this field. This paper investigates the design considerations and development of the stringed chordophone and specifically the guitar. The challenge is to produce a mechatronic device capable of speedy and reliable note selection, string actuation, string damping and expressiveness. In the same manner that there is not one best way to play a guitar and no best guitar design, so too is there no ''best'' chordophone design. Rather, the competing factors of speed, precision, reliability, portability, expressiveness and timbral variation can be given different weightings and result in different designs. Therefore, rather than presenting a single chordophone development, this paper provides a multitude of design options providing an interested reader with the background and suggestions to create their own bespoke design. This paper concludes with the presentation of the authors' final design as an integration of the presented ideas and design techniques. We demonstrate that this chordophone introduces expressivity at a level not achieved before, is modular yet portable, is mechanically quiet and can play at a speed beyond that of even the best human player. INDEX TERMS Automated music production, mechatronic chordophone, mechatronic music.

The Design and Construction of an Expressive Mechatronic Chordophone

“…Generally, mechatronic chordophones have integrated the MIDI hardware specification into their systems' input and output using MIDI messages, and 5-pin DIN connectors into their boards as MIDI In and MIDI Thru 4 [47,42,31,34]. In Protochord, we refrain from using this approach, and instead take advantage of increasingly available computer software for human-robot interaction, in particular the specialised development frameworks such as Max MSP 5 , as well as open-source alternatives including Pure Data 6 and ChucK 7 . MIDI controller keyboards and surfaces have also adopted USB connectivity widely.…”

“…Furthermore, this servomotor features angle limiting capabilities, which is useful to constrain the robot arm's displacement range, and therefore avoid the kinematic singularities discussed in Section 4.3. We communicate with the Dynamixel using a half-duplex UART 5 , with a single data line. The data line goes through a SN74LS241N Tri-state Buffer which is connected to the TXD, RXD, and a data control pin of our Teensy 3.5 microcontroller.…”

“…The koto is a classical Japanese stringed instrument similar to a zither or a lap steel guitar 5. Counterpoint is the relationship between independent musical lines, which are harmonically related.…”

The Design and Construction of an Expressive Mechatronic Chordophone

“…However, mechanical noise can become a problem if it is loud enough to overpower the instrument's acoustic sound, particularly if the chordophone can only be heard through speakers at high volume levels. Recent chordophones have been designed to maintain noise levels below 60 dB [50], which is usually considered to be the volume of a quiet conversation in a restaurant or office 5 .…”

“…There are few choices of optical pickups at a commercial level. These include the LightWave optical pickup system 4 , Taff optical pickups 5 (for upright bass and cello), and Light4Sound'sōPIK optical guitar pickup 6 (which is still under development). Furthermore, these transducers have not been documented extensively in mechatronic music literature, however, they have been used in Trimpin's guitar sculptures [1], as well as BassBot and MechBass (discussed in Sections 5.4.1 and 5.4.2 respectively).…”