The electric guitar is in many respects the ideal instrument to augment, modify or hack. It's cheap, rugged and widely available, and its sound can be altered, modified and processed to a profound degree. Also, as electrical amplification is an inherent part of the instrument these modifications can be achieved with relative ease compared to traditional acoustic instruments.
Effects pedals are by far the simplest and most familiar way of changing the sound of the guitar, and other instruments too. There are many different types of effects available and there are also many DIY electronics workshops and online resources to help you build your own. This page will however look at some of the less well known ways in which we can modify, augment or extend the capabilities of the electric guitar, using everything from screwdrivers and bows, to microphones and electromagnetic pickups, and smartphones.
One of the first composers to explore the preperation of instruments was the composer John Cage in his various works for prepared piano. The preparation in this case consists of various objects inserted between the strings of the piano, drastically changing its sound as we can see in this video.
Norwegian composer and guitarist Bjørn Fongaard was one of the first to adapt this idea to the electric guitar, and he went on to develop a wide range of prepared guitar techniques. In this beautiful performance from 1971, Fongaard performs a work for Micro Intervallic Guitar using just fingers, a bow, and an unusual tuning scheme to radically alter the sound of the instrument.
This type of traditional preparation has been developed over the years and there are now many, online resources about this technique. Of course with the guitar we can also use different objects and devices to play the strings, as well as modifying the sound by placing objects between, on, or under the strings. In this wonderful video, guitarist/composer Roger Kleier demonstrates a number of these techniques and discusses his initial motivation to his work with the prepared guitar.
When using preparations or non-traditional playing techniques, it is often easier to place the instrument on a flat surface, rather than holding it in the traditional way. As Kleier mentions, some players just use their lap so they can switch to normal position if they wish, while others prefer to use a tabletop guitar. For the guitarist and painter Keith Rowe, this shift in playing position was far more profound than a simple practical necessity. Inspired by the visual arts and particularly Jackson Pollock's technique of painting with the canvas lain flat on the floor, Rowe has developed a distinctive and innovative style that has been highly influential.
Another important technique developed by Rowe, and later most notably by Fred Frith, is the 3rd bridge guitar, and this again leads to a fundamental shift in change in how we approach playing the instrument. By dividing the neck into two using a capo, screwdriver or pencil, we can effectively create two guitars which can be plucked with each hand, almost like a zither. This technique can produce really beautiful timbres due to the way in which a string plucked on one side the 3rd bridge produces subharmonic resonances in opposite side. When the bridge is placed at a harmonic position this results in a especially clear, bell-like consonant multiphonic tone.
The work of composer Harry Partch on microtonal theory using is own unique instruments was a significant influence on a number of composers, guitarists and luthiers such as Glenn Branca, Thurston Moore and Lee Ranaldo of Sonic Youth, and Yuri Landman. The Moodswinger and Homeswinger, designed by Landman, are perhaps the fullest expression of this idea to date, to the point that they more closely resemble electric zithers than guitars. The relationship between this instrument, the just intonation theory of Harry Partch, harmonic tuning schemes, and punk rock experimentalism is nicely outlined by Landman in this article, entitled "3rd Bridge Helix - From Experimental Punk to Ancient Chinese Music & the Universal Physical Laws of Consonance".
Dividing the guitar into two in this way naturally suggests another type of modification, namely the addition of an extra pickup to independently amplify each set of strings. This type of stereo guitar has a few precedents, and more recently the development of hexaphonic pickups has extended this idea to the amplification and processing of each individual string, i.e. the polyphonic guitar, the topic of the next section. The following piece is an example of an improvised 3rd bridge guitar using a pencil (screwdrivers can be effective too) at the 5th harmonic position (the 9th fret), and a similarly improvised additional pickup, mounted (ish!) at the neck (see the next section for more sophisticated implementations).
The guitar contains a third bridge (a pencil) at the 5th harmonic position just behind the 9th fret. Screwdrivers can also work well, particularly if the required position is away from the frets. In this case, the 5th harmonic position used is just behind the 9th fret, so a hexagonal pencil can be nicely balanced half on the 9th fret with a pointed end making contact with the strings. Choosing this position gives us the 5/2 and 5/3 harmonic intervals above the open string, which is a harmonic major 3rd (on the bridge side) and a harmonic major 6th (on the neck side).
As tabletop guitars like this are often played with different physical objects, I thought it would be interesting to experiment with using digital models of physical objects (in this case a pendulum) to virtually play the instrument, in a way which is not really physically possible in real life (for more technical details on this piece, click here).
The title is a reference to the type of divination known as dowsing and its associated use of pendulums and maps. The apparently spooky movement of a ouija board, diving rod or pendulum is of course a result of reflexive, miniscule muscular reactions which can be outside of the awareness of the person in question, which is perhaps just a little bit like improvising music.
The pickup itself opens up a whole other range of interesting playing techniques and instrument modifications. Standard electromagnetic pickups can react in interesting ways to devices like hand-held electric fans, radios, or magnets, and interesting feedback and sustained sounds can be created using electromagnetic sustainers, either handheld devices like the well known ebow, or built into the guitar.
For 3rd bridge guitars, adding a second pickup to the neck position is very useful. Fred Frith was one of the first guitarists to explore this idea, using an aluminum harness bolted onto the neck to hold the pickup in place above the first fret.
Of course we can also divide up the strings in a different way, by using a special pickup to amplify and perhaps process each string individually. The earliest implementation of this idea goes back to the 1960s and the Gretsch White Falcon which used two pickups to separate the upper and lower three strings into two outputs. You can hear this stereo effect very clearly on many of tracks on Neil Young's 2010 album Le Noise.
This idea can be taken further using a hexaphonic pickup which provides six discrete outputs, one for each string. The multi-channel output of these pickups is often solely used for conversion to MIDI, however, the six string signals can also be processed in many different ways. Recently polyphonic fuzz and modulation effects have emerged, and real-time processing of six signals using a computer is now quite achievable using a suitable multi-channel soundcard. One interesting approach is to position or even move the individual strings between multiple loudspeakers positioned around the audience, something which I often explore in my own work.
The easiest way to obtain a hexaphonic signal from an electric guitar is to use a MIDI pickup such as the Roland Gk-3, as these can be non-destructively added to an existing instrument. RMC hexphonic pickups are installed under the bridge (often in Godin guitars) and these piezo-based pickups give quite a different sound to the Roland devices (which are traditional electromagnetic designs). Regardless of the pickup itself, most popular guitar MIDI systems use Roland's 13-pin connector system, which passes a hexaphonic signal to an external device for conversion to Midi. This same type of connector is now also used for polyphonic effects units such as the Spicetone 6Appeal.
To access these signals for audio processing, a simple breakout box can be constructed which simply connects the wires from pins one to six to six 1/4 inch jack sockets. Other breakout boxes include the Spicetone fuzz pedal (which is also a high quality breakout box), and the Septar board by Ricky Graham.
Rolands 13-pin system (left) and Custom Breakout Box (right). www.unfretted.com
For an excellent tutorial on how to construct such a breakout box go to www.unfretted.com, while a more detailed look at this topic can be found in the paper Adapting Polyphonic Pickup Technology for Spatial Music Performance.
Augmenting musical instruments with additional sensors to capture and utilize the physical gestures of the performer is not a new idea, however, it has never been easier (or cheaper) to create these types of hybrid instruments.
Recent years have seen the arrival of a variety of different devices which can track movement. Examples include game controllers like the Nintendo Wii and Microsoft Kinect, mobile devices and smart phones, and dedicated sensors like the Phidgets range. It is now reasonably straightforward (and importantly affordable) to adapt these devices to detect the position, orientation and movement of the instrument and/or performer. The information from the sensors can be sent to a laptop and used to process the audio in a variety of ways, or to generate live visuals.
Hans Tammen has developed a sophisticated performance system based around a hybrid guitar/software instrument known as the endangered guitar. In performances, the guitar functions simultaneously as a sound source and controller for the electronic processing, often with a significant spatial component. One effective and quite simple technique developed by Tammen is the use of an iPhone as a slide while using the devices accelerometer data to also control the electronic processing.
I developed a prototype augmented guitar system for a Creative Lab at the 2013 New Music Dublin festival using a Max MSP, an iPod touch and a Phidgets sensor board. The iPod was attached to the guitar and this transmitted information about tilt and orientation to the computer using the freeware gyrOSC application and an ad-hoc wireless network. In addition, a Phidget Spatial board was also used to detect the position and motion of the right hand and transmit this information back to the laptop via USB.
Both the iPod and Phidget primarily use 3-axis accelerometers and gyroscopes to detect the movement and orientation of the device. Although a much more accurate tilt reading can be obtained using these two sensors in combination, this is not possible on the Phidget board as the magnetic field around the humbucker pickup on the guitar severely distorts the gyroscope readings when ever the right hand passes by. It does mean however that the proximity of the right hand to the pickup, and thus the strings, can easily be detected and this very simple proximity detector can be highly useful.
The software detects when a note has been plucked, it then sustains and processes the sound while the position of the right hand is used to spatially pan the sound around the loudspeaker array. A downward strum moves the sound from the front (at the guitarist) to the left, while an upward strum moves the sound to the opposite side. The further the hand moves up or down, the further the sounds moves around the array.
Moving the right hand close to the magnetic pickup fades up a low, harmonic drone while striking the guitar body causes this sound to rotate and tremolo. Similarly, tilting the guitar forward introduces an additional drone which can be rotated to either side by tilting the guitar left or right.
The piece itself is based around the harmonic series on C, and the guitar is tuned to a harmonic tuning with a 'flattened' 3rd and 7th (tuning from low to high: C G C E (-14 cents) G Bb (-31 cents)).
This piece was recorded using a binaural microphone so for best results, listen back on headphones.