Jon Zs

CRO (cathode ray oscilloscope); Laser and Electronic music

Background info

Initially, cathode ray oscilloscope is one of the most versatile tools for the development of electronic circuits and systems, the most commonly used in medical district such as the heart beat detector in hospital. Nowadays, many musicians (mainly from the electronic music industry) use CRO as their compulsory instrument or equipment. Music wise, there are some of the basic characteristics of the CRO’s components:

CRT – the cathode ray tube which emits electrons to the phosphor screen to display a signal, this function could be used as the visual effects during the production work and live performance by musicians; by connecting the output of CRT to various of massive screen or LED stage lighting system, it can produce one of the best visual effects, which the best to be known is the green color laser.

Vertical amplifier – a wide band amplifier used to amplify signals in the vertical section. Musician can adjust the sensitivity (gain) and frequency bandwidth (BW) which response characteristics of the oscilloscope.

Delay Line – It is used to delay the signal for some time in the vertical sections. Sometimes musician uses this function in one of the audio FX in art work.

Time Base – It is used to generate the saw tooth voltage required to deflect the beam in the horizontal session. It provides the option for musician if who want to use the original CRO saw tooth wave as the main sound source.

Horizontal Amplifier – it is consisted with the Time Base Generator, this is used to amplify the saw tooth voltage before it is applied to horizontal deflection plates. Musician use it as an output to amplifier, which normally connects to the PA system during the live performance.

Trigger circuit – Convert the incoming signal into trigger pulses so that the input signal and sweep frequency can be synchronized. When CRO generates the signal, the circuit uses the continuous sweep, when attempting to display voice or music signals, the pattern falls in and out sync as the frequency and amplitude of the music varies resulting in an unstable display. The most common example is the green color laser synchronised with sound waves to produce the unstable and changeful waveforms.

The Pioneers

In early 1960’s, Ben F. Laposky, an American sound/electronic engineer commenced in his article “Electronic Abstractions” about the cathode ray oscilloscope, “ they are compositions of electrical vibrations in light as pleasing to the eye as composisions of sound vibrations in music are pleasing to the ear. These beautiful visual thrythms and harmonies of electronic abstract art maybe recorded by means of photograph.”

He also commenced “ The oscilloscope is highly versatile and has a number of controls which modify the size, shape, brightness and position of the races which appear on the “scope screen” this trace is formed by the impact of a beam of electrons on the inside of the phosphorescent face of the picture tube. It travels very fast across the screen, but because it retraces itself many times a second and because of the nature of the screen a continuous line or form is seen by the eye or camera.

Through the development of variety of electronic circuits inside of the CROs in early 1960’s, different types of CRO could produce few sound waves such as sine-wave, sawtooth-wave, square-wave, and lissajous figure.

All of these sound waves may be combined and modified in many ways by electronic instruments (e.g. synth) to form designs or patterns, so that the operator of the variously assembled setups has a large measure of creative control over the resulting traceries which appear on the oscilloscope screen. Therefore, artist can combine different sound waves in order to compose several of visual forms and textures, and a greater amount of choice in shaping the final composition.

An exhibition was organized and mounted by W.D. Frankforrer, director of Sanford Museum, and by Laposky. The picture below is few examples that show the arrangement of the introductory sections and mounting of the photographs.

As observed in the exhibit explanation, there is an interesting parallel between these art forms and music. The operator of an electronic setup crating them may almost be said to play a kind of “visual music” with it, especially when the moving traces on the oscilloscope screen pulsate rhythmically or harmoniously expand and contract in a kind of crescendo and diminuendo. Since much music is not representational of any sounds in nature, and so is abstract, the analogy with these electronic designs follows in yet another way. It is interesting to note, also, that many electric organs and other electrical musical instruments incorporate electronic oscillators, amplifiers, and other circuits which are similar to those used in this visual technique.

The Practitioners

Dr. Robin Fox is a Melbourne based sound and visual artist currently working with live digital media in improvised, composed and installation settings. He creates audio-visual works for the cathode ray oscilloscope, which have been released on the DVD ‘Backscatter’ (synesthesia records).

Dr. Robin Fox is best known for his synaesthetic performances with laptop and laser beam, of course with the combination of CRO. He uses an audio controlled laser projector to demonstrate the geometry of sound was as elegant as anything people might experience in a concert hall or gallery. People call Dr. Robin Fox the “ZZ Laptop” because he explores the synchronisation of sound and image by linking his laptop bass textures to a CRO and it links with a single-point laser, projected through smoke as series of violently cut-off changes in shape and form.

In Fox’s live performance, an oscilloscope links with laser beams, they produce the green fluro trace flattens out to a straight line, that line like a bolt from the proscenium wall across the audience multiplying as it describes an astonishing variety of planes, with the portentous hiss of a smoke machine and few mirrors, the venue emerges into a 3D space with rapidly changing green laser spectrums which synchronized with various of sound waves.

The sound-image relation Fox presents in his live audio-visual performances is at work in these photographs, silent as they necessarily are. Fox exposes the infinite complexity of any seemingly simple object or phenomenon. He offers us a synaesthetic variant of the ‘optical unconscious

Fox’s images give us tools to hear differently: where notated music reifies certain set of frequencies into a group of objects, in Fox’s work even a single sine tone is revealed to be an abstraction from an ‘immense number of events’. In the representations given to us by the oscilloscope or Fox’s laser, the material reality of sound appears as a massive complexity that always transcends human perception.

CRO has enabled humans to convert electrical signals into waveforms, and therefore made it easy to see the pattern of the wave. By knowing the pattern, frequency and amplitude, scientists and engineers can better understand and control the behavior of electrical systems. It is a powerful device; Musician can use CRO to create visual and audio syncronisational effects and stage light artist can also benefit on using it for live performances, it enables the laser lighting designer to create patterns such as lissajous figures.

The laser light display on live performance, fully emerged in recent years and became a form of psychedelic entertainment, usually accompanied with a live musical performance on stage or pre-recorded music. Pink Floyd and The Who were among the first high-profile rock acts to uselasers in their concert shows. Blue Öyster Cult also used laser shows on tours that supported their album Spectres, which shows a staged portrait of the band members seated among the laser beams, and Electric Light Orchestra made use of lasers during their 1978 Out of the Blue Tour which also featured the famous “Flying Saucer”, This is now highly regulated in the U.S., to the point where almost no U.S. shows have laser beams that go into or close to the audience. The Legendary electronic music group Daft Punk released a DVD “Alive”, the concert filled up with massive LED laser beams which controlled by their instruments and stage lighting crews.

References

BENP 2183 Electronic instrumentation, Chapters 3 Oscilloscope, Viewed 11 April 2011. http://benp2183.mazran.com/download/nota_kelas/chap3_oscilloscope.pdf 

Robin Fox, 2011, Robin Fox site, Plum Industries, Viewed 17 November 2011 http://www.robinfox.com.au/about/

 Robin Fox, 2011, Robin Fox site, Plum Industries, Viewed 17 November 2011 http://www.robinfox.com.au/press/

 Ben Gook, Autistic Daughters, Sunday Jan 14, 2007, Mess and Noise Magazine Melbourne VIC Australia.

 Sumugan Sivanesen, 2009, Resonate on-line magazine, Sydney NSW.

 Penny Webb, “Robin Fox” 2007, the Age Newspaper.

Jonathan Marshall, 2007, ‘Vertiginous pleasures of disconnection’, Real time Magazine issue #79 June-July 2007 page 40.

Wikipedia.org ‘Laser lighting display’, viewed 13 April 2011. http://en.wikipedia.org/wiki/Laser_lighting_display

Francis Plagne, 30 July 2010, ‘Robin Fox – Proof of Concept’, booklet of the exhibition Robin Fox.

Ben F. Laposky, 1974, ‘Oscillons’ Electronic Abstractions, A new approach to design, Cherokee, Iowa.

Robin Fox, 2011, ‘Sound and light signal simultaneity’, Issue 66, filter.org.au. http://filter.org.au/issue-66/sound-and-light-signal-simultaneity/