Points of Contact by Erfan Abdi

Erfan Abdi in the bird cage, performing Points of Contact at STEIM.
Erfan Abdi in the bird cage, performing Points of Contact at STEIM. © Erfan Abdi

Big eyes as contact microphones, a bird cage as a loudspeaker, and two double spring objects of which again one functions as a loudspeaker and the other as a loudspeaker: this is the inventive set-up Erfan Abdi uses for his performance Points of Contact (2017). Erfan himself seems to be a bird, placed in the cage to perform for us, gently trying to break out by touching the bars with his metal eyes.

The sounds during the performance are created by different combinations of the same set-up: both amplification as well as feedback through the contact microphones and tactile transducers are used. By using additional long springs the different elements can be connected to each other. To give an example of one of the many possibilities for doing all kinds of physical signal processing with this set-up: a signal of the big eyes contact microphones is sounding through the bird cage transducer, and since both are touching each other a feedback loop occurs (1 in the scheme below). The bird cage is also connected with a spring (2) to the double springs with a contact microphone (3). This is amplified through the transducer attached to two double springs (4). This is fed back again to the double springs with a contact microphone (5) by connecting the springs with the help of again an additional spring. The sound of all contact microphones is also amplified by the two main loudspeakers in the hall (the PA system) (6).

transducer exciter contact mike microphone Erfan Abdi
Set-up scheme for Points of Contact by Erfan Abdi, see the description above for a detailed explanation.

What makes this set-up so versatile for producing all kinds of different sounds, is that the two feedback loops can both be combined, influence each other but also broken up again (the first feedback loop are the contact microphone eyes and bird cage transducer, and the second the springs contact microphone and springs transducer). Take away, for example, the spring in between the two double springs—(5) in the scheme above—and the double springs become a spring reverb for the sound produced by the bird cage feedback. The whole set-up is constructed in search for fragility and inaccuracy in response to the feedback signal. For this reason, the two contact microphone springs have been chosen by Erfan because their frequency response is slightly different: this results in a modulating feedback sound instead of a feedback on one constant pitch.

The two contact microphone eyes
The two contact microphones are enlarged by small metal plates so they can touch several bars of the bird cage at once. © Erfan Abdi

For the same reason the contact microphones eyes are made by simple piezo disks placed on round metal plates: this gives the possibility to touch the bird cage at two or three bars. As Erfan explained me, when there is just one point of contact between the contact microphone eye and a bird cage bar the feedback tends to be especially strong on the fundamental frequency of the pitch. But as soon as you touch two or three of the bird cage bars, more partials are added to the sound. And by using two contact microphone eyes they also start to modulate each other. The placement of the contact microphone below the  two springs is again aiming for a richer and less stable sound: instead of having just a single point of contact, the whole disk is touching as much as possible of the surface of both springs.

The contact microphone beneath the springs. © Erfan Abdi
The contact microphone beneath the springs. © Erfan Abdi
The contact microphone beneath the springs. exciter body shaker
The tactile transducer underneath the two other springs. © Erfan Abdi
The tactile transducer bird cage exciter body shaker
The tactile transducer attached to the bird cage. © Erfan Abdi

Erfan uses the music software Reason to do some processing of the feedback. Basically it provides a compressor, a delay line and an amplitude follower. The amplitude follower is used for modulating the delay time, so as soon as one frequency gets too loud, the delay is changed, and the frequency of the feedback will also change. The connections between the different parts of the set-up—which contact microphone is connected to which transducer etcetera—is controlled live by Erfan with a small MIDI controller.

During the performance Erfan is sitting in the cage, an intriguing image for a music performance. The movements of his head towards the thin cage bars seem to underline the scenery of a bird locked in against his will. But it is with the resulting sounds that this bird seems to be able to leave the cage: the variety of sounds not only enlarge the musical possibilities of this set-up, but also give the impression that the music can sonically fly away from the cage. The bird might seem to be locked in visually but sonically it is free to come and go.

Below you can view some short fragments of Erfan Abdi performing Points of Contact at STEIM in Amsterdam, and listening to a recording of a performance excerpt. And if you are close to The Hague: Erfan performs a new version of this piece tomorrow (Thursday 10th of October) at Ephémère at Studio LOOS.

Touche Nature by I-lly Cheng

We Spoke plays Touche Nature by I-lly Cheng
We Spoke plays Touche Nature by I-lly Cheng. © I-lly Cheng.

Vibrations of loudspeaker membranes cause air pressure waves, which our hearing system perceive as sound. As long as they are travelling through the air, these sound waves stay invisible to human beings. But as Ernst Chladni described in his book Entdeckungen über die Theorie des Klanges already in 1787, sound can be visualised by bowing a surface lightly covered with sand. So-called Chladni patterns are produced in this way. In her piece Touche Nature (2017) I-lly Cheng creates a phenomenon similar to Chladni patterns by placing transparent bowls filled with water on loudspeakers. The sound waves are visualised as water waves:

A bowl filled with water is placed upon a big loudspeaker in I-lly Cheng's piece Touche Nature
A bowl filled with water is placed upon a big loudspeaker in I-lly Cheng’s piece Touche Nature. © I-lly Cheng

A contact microphone is attached to the bowl and amplifies the bowl itself and the water movements in the bowl. Four percussionists each play a bowl filled with 1000 ml of water. During the performance the percussionists produce sounds by moving the water with their hands, rubbing the bowl, throwing stones in the bowl or pouring more water in the bowls. These sounds are all picked up by the contact microphones and then amplified  through the PA system. The water sound itself is also picked up by four condenser microphones and amplified directly through the loudspeakers in the hall.

The first page of the score of Touche Nature by I-lly Cheng.
The first page of the score of Touche Nature by I-lly Cheng (for the attentive reader: in the original version 500 ml water was used, but this was corrected to 1000 ml). © I-lly Cheng

As the first page of the score shows, the sound is processed with a pitch shift effect in the computer and there is also some feedback used. The feedback is created by sending the signal of the contact microphones back to the four loudspeakers underneath the bowls. There is no direct feedback happening though, but a pair of two loudspeakers and two microphones is together producing one big feedback loop.  The sound picked up by the contact microphone of player 1 is sent to the loudspeaker of player 3, which is then picked up by the contact microphone of player 3, creating a feedback loop by sending it to the loudspeaker of player 1. The same feedback is created between player 2 and 4.

An overview of the loudspeakers and contact microphones used in Touche Nature. The four condenser microphones used for direct amplification of the water sounds are not on the picture.
An overview of the loudspeakers and contact microphones used in Touche Nature. The four condenser microphones used for direct amplification of the water sounds are not on this picture. © I-lly Cheng

You can hear different kind of effects, including some feedback, at the very beginning of the piece, performed here by We Spoke:

During the piece I-lly explores the sonic world between natural water sounds and more abstract percussive rhythms. At the end of this fragment some pre-produced sounds are played through the loudspeakers, creating big movements in the water. These movements can not only be seen but the water sound caused by these movements is amplified through the condenser microphones. The loudspeakers seem to become liquid themselves:

Small Movements by Adam Basanta

Adam Basanta performs Small Movements.
Adam Basanta performs Small Movements. The performance starts with acoustic feedback by holding a very small loudspeaker close to a microphone. Video still. © Adam Basanta

In his set-up for Small Movements (2016) Adam Basanta uses two microphones and seven loudspeakers in different combinations to create acoustic feedback. The sound of the feedback is surprisingly “clean”: it contains not much noise, but focuses essentially on a single pitch. This is no coincidence, because besides the seemingly chaotic set-up of all kinds of glass jars, wires and cassette players he uses the music software Max  to control the resulting sound precisely. There is a constant interaction between the physical sound creation with the objects on the table and the virtual sound control in the computer.

Set up for Small Movements by Adam Basanta
Set up for Small Movements by Adam Basanta. The grey circles are the seven loudspeakers. The two other microphones on the pictures and video are used for general amplification of the sound through the PA system. © Adam Basanta

Let’s first have a look (and listen) at how Adam uses the objects on the table to influence the sound. As mentioned before, acoustic feedback is an important element and an example of this can already be heard at the very beginning of the documentation video (you find the video at the end of this post). Physical interaction is done also by putting a stick on a loudspeaker membrane (see 15’44” in the video). On a later occasion Adam uses a metal wire (16’40” in the video). Due to low frequency sine waves sent from the computer to the loudspeaker (more on this in the part on the computer software used), the membrane will move back and forward and the stick or wire jumps on the membrane, causing a quick rhythm. The jars are used as what could be called a physical filter. By placing them on or close to a loudspeaker, the sonic outcome is influenced by the resonance frequencies of the jar (see 14’15” in the video). By holding a jar close to a microphone, the microphone picks up the resonance frequency of the jar and the pitch of the feedback will change (see 20’30” in the video).

Adam Basanta uses a jar for preparing a loudspeaker.
Adam Basanta places a big jar above a loudspeaker to change the feedback frequency. Video still. © Adam Basanta

This physical sound creation is now enhanced by the use of a computer software. A patch created in the music software Max manipulates the signals coming from the microphones before they enter the loudspeakers. I asked Adam what kind of sound processing is going on and he let me know that “Of course, there is some serious limiting on each channel, calibrated to each speaker’s capacity in order to avoid burning them out. But the main processing occurs through two algorithms, which regulate the feedback frequency and amplitude. For frequency, I use various filtering techniques, […] which only allow feedback to occur at specific frequencies. Filtering can allow very precise control of the frequencies, and also allow me to create feedback in ways which are very unfamiliar to us: for instance, very low frequency feedback, or a tonal triad using feedback.” The processing is thus not only keeping the feedback within reasonable loudness and avoiding damage to the loudspeakers. With the help of a Max patch, the feedback frequencies are fixed quite precisely: 14 different pitches can be played by using the 14 possibilities of feedback between the two microphones and seven loudspeakers. And with use of a foot pedal Adam can switch to another preset in the Max patch, giving him a new row of 14 different pitches.

Score Adam Basanta Small Movements
Adam Basanta uses his set-up for Small Movements also for other projects, such as a piece with bass saxophone player Jason Sharp. The score illustrates how accurately the set-up can be played. (The cup of coffee is just part of the developing process…) © Adam Basanta

In Small Movements different kinds of technologies are used in undogmatic ways. Although you might have the impression, that you see all sound processing happening, much is done by help of virtual sound processing in the computer. Besides the heavy filtering of the feedback sound, the low sine waves mentioned earlier are  another example of sonic material generated by the computer. By using these low frequency movements of the loudspeaker membrane to “play” a stick or metal wire Adam connects the computer software to the physical sound production.

Two cassette players belong also to the set-up on the table, playing back the material just produced by the performer. In Adam’s words: “The cassette looping is kind of a layer on top. The cassette players themselves are quite old, and so I use them as a way to echo or repeat previously occurring material, but in a way that is quite degraded. They are mostly used as faded memory of material which was crystal clear at the time at which it was played.”

Sound in a Jar by Ronald Boersen

speaker jar microphones
Different microphones are used to pick up the sound from the small loudspeaker in the jar. © Ronald Boersen

In Sound in a Jar (2016) by Ronald Boersen three performers— Ronald Boersen himself, Dganit Elyakim and Hadas Pe’ery—move three different microphones back and forwards to a very small loudspeaker placed in a jar. As Ronald explained me, this piece is a sound environment, which changes and developes algorithmically during the performance. The main task for the performers during the rehearsals is to explore this environment and find ways to engage musically with the sounds they can produce. The performers pick up the sounds of the loudspeaker in the small jar and it is sent back to the loudspeaker again, passing through a patch in the music software Max. By placing the loudspeaker in a jar, the sound will resonate easier, a very suitable feature for acoustic feedback. The main sound of the performance is thus acoustic feedback, coloured by the different characteristics of the three microphones used (two different condenser and a dynamic microphone).

microphones loudspeakers max msp
This scheme gives an overview of the inputs and outputs of the piece, as well as the three forms of live processing used, in form of a Max patch. © Ronald Boersen

The Max patch processes this feedback sound: as the scheme depicts, Ronald uses threshold triggered reverb pulses, feedback interval driven harmonisation and granular delay lines. By using amplitude thresholds and feedback frequencies these processes are directly influenced by the feedback sound itself, and the feedback itself is processed by the Max patch. In this manner Sound in a Jar uses a double form of feedback: acoustic feedback (using the sound itself) and data feedback (by using data streams generated from amplitude and frequency analyses of the loudspeaker sound, without using the sound itself), and both are effecting each other constantly. How much the sound of each microphone is processed by Max and which of the three processes is used (reverb pulses, harmonisation or granular delay) is changing during the piece, as is depicted in the diagram in the score. The relationships between microphone, processing and loudspeaker change not only accordingly to the distance between microphone and loudspeaker but also because of the temporal development of the kind of sound processing in the Max patch.

In this close-up video the development in sound processing and the direct relationship between the movements of the microphones and the resulting sound can easily be followed:

A very appealing aspect of this set-up is in my view, is that all three microphone signals are connected to a single loudspeaker. All three players have to find their own way of playing, because they have a different type of microphone and their sound is processed in a different way, but at the same time all these different paths come together again in a small loudspeaker in a jar. In the second part of the performance the sound of the small loudspeaker is slowly also diffused through the bigger loudspeakers in the hall (the PA loudspeakers). This does not cause any noticeable change in the acoustic feedback interaction, but the spatial and spectral characteristics do change due to the different in placement, sound diffusion and spectral response of these loudspeakers. The sound of the jar itself seems to fill the whole performance space now, instead of occupying a single spot. At the end of the piece, the loudspeakers in the hall fade out again and the sound moves back into the jar.

By preparing this text I also discovered that Ronald Boersen has an interactive sound installation, that uses loudspeakers and ping pong balls. I added this to the collection of fifty years of loudspeakers and ping pong balls.

And here a recording of the whole piece: