Strings, brass, percussion, woodwinds… yawn. We’ve been making music with these instruments for the longest time – but the last 100 years have seen the emergence of some new forms of instruments thanks to the advancement of technology. Here are five innovative ways to make and control music and the science behind how they work.
1. Lightning
We’ll kick off this list with what is undoubtedly my favorite application of technology to musical purpose: the singing Tesla coil. Sometimes called the zeusaphone or thoramin after ancient gods of lightning, this mad scientist’s contraption is a Tesla coil modified to serve as a plasma speaker.
There is no physical speaker here – the sound is produced directly from the electric arcs. Conventional speakers work by vibrating a physical diaphragm – generally a thin membrane – which in turn moves the air around it, propagating a sound wave. To use a simplistic example, imagine striking a bell, or tuning fork. While the object is vibrating, you hear a tune. But stop it from vibrating by touching it, and the tune stops.
How does electricity produce sound without a physical diaphragm? The same way a bolt of lightning does. When an electric current discharges through the air, be it as a bolt of lightning or as a man-made occurrence, the air through which it travels is near-instantaneously superheated into the fourth state of matter: plasma. By the gas laws we learned in high school, we know that an increase in temperature without an increase in volume results in an increase in pressure, so the electric arc is a high-temperature, high-pressure plasma channel. Since the air around this channel is of lower pressure than the plasma channel, the plasma rapidly expands into the surrounding air, producing a shock wave, or sonic boom, that propagates through the air – not unlike a physical diaphragm.
By modulating the spark output of a Tesla coil, you can control the precise pitch of the electric sonic boom and produce some rudimentary sounds – enough to play simple MIDI tunes, like from all our favorite retro video games.
Something that doesn’t always come across in the YouTube videos is how loud zeusaphones are. Some measurements have placed the sound output of these behemoths at 120dB. To put that into perspective, sandblasting or a loud rock concert measure in at 115dB, and at 125dB, pain begins.
2. Lasers
From lightning, we’ll move onto the laser harp. In this case, the laser doesn’t serve as the mechanism that produces the sound, but rather as the human interface device for playing the instrument.
The laser harp is connected to a device that will interpret the commands and play the sound – generally a synthesizer or computer. Lasers emulate harp strings, fanning out from a laser emitter, and when one of the laser beams is interrupted, a note is played. While some laser harps keep things as simple as that – block a beam with your hand to play a note – some measure the position of your hand to allow you to modify the pitch or even simulate the vibration effect of an actual stringed instrument.
How does the laser harp know whether you’re blocking a laser beam, and how far along the beam your hand is? By using either a photodiode or a USB camera. The laser harp doesn’t actually recognize that the laser beam is being broken – rather, it looks for the light that the laser beam would produce on a hand interrupting it. The USB camera is self-explanatory, but the photodiode is a strip of semiconductive material angled behind the laser emitter such that it will detect the telltale bright spot of a laser beam striking a hand. When the reflected light of the laser on the hand bounces back and strikes the photodiode, the photons are converted into an electrical current that signals that a note is being played.
But the photodiode isn’t a camera – it doesn’t know which note is being played, only that some note is being played. It’s just a photon receiver. So how does the harp know which note to play? It’s all about timing. While it may appear that all the lasers are being emitted simultaneously, they are, in fact, each being turned on and off at specific times. Too fast for the naked eye to perceive, the strobing effect is caught by the sensitive photodiode and the controlling device. This means that when the photodiode says “Hey! I got something!” there is only one possible laser beam that can be “on” at the precise moment in time.
3. Electromagnetic Fields
We can’t talk about weird human interface devices without talking about the theremin. If you think you don’t know what a theremin is, you should be happy to note that you are mistaken – it lent the otherworldly operatic singer “woowooooo” sound to the original Star Trek theme and punctuated the soundscapes of countless old horror and sci-fi classics.
A theremin consists of two metal antennas that detect the position of the player’s hands. The distance from one antenna determines the pitch of the note played, while the distance from the other determines the volume, and sound is output through a speaker.
When we talk about pitch and volume, what we actually mean is the frequency and amplitude – respectively – of the resulting sound waves. Picture your basic sinusoidal wave being broadcast on an oscilloscope. The wave’s amplitude is its “height” – the vertical distance from crest to trough. The greater a sound wave’s amplitude, the louder it is. Frequency isn’t exactly a measure of a wave’s width (the horizontal distance between two crests), but the width of a wave directly relates to its frequency – the wider a wave, the lower its frequency, and the deeper its pitch.
How do the antennas know where your hand is? First off, they are not actually antennas, since they are not used for either broadcasting or receiving a radio frequency. Instead, they serve the same role as plates in a capacitor.
Put simply, a capacitor is a device that maintains an electromagnetic field between two electrically conductive plates. In the case of the teremin, you may think that the two antennas correspond to the two plates that form an EM field, but that’s not the case. Each antenna serves as a plate for a separate EM field – and your hands serve as the other plates. The distance of your hand from the antenna determines the capacitance of the EM field – how much energy is stored within it.
4. Vacuum Tubes
If you thought the theremin was a weird instrument, then the ondes Martenot will really freak you out. Cousin to theremin, the ondes also has an eerie sound and functions by varying electrically-generated wave frequencies. But it departs from its antennaed brethren in its method of being played: by slipping your finger in a ring that is attached to a string and moving your hand along the length of the string, which vary the oscillation frequency of sound waves generated in a vacuum tube.
A vacuum tube is a vacuum-sealed container through which an electric current runs. That current is generally created by a filament, like a light bulb, and early vacuum tubes in fact evolved from incandescent light bulbs. Through an effect called heterodyning, two high-frequency radio waves – inaudible to the human ear, of course – combine to create an audible wave of a frequency equal to the difference between the two radio waves.
As with the theremin, the human body affects the capacitance of the resulting electromagnetic system and thus affects the frequency of the sound wave. But rather than have you wave your hands around like a crazy person, the ondes has you tether your hand to a string that runs the length of a keyboard by slipping your finger in a ring. The keys could either be played directly to produce fixed notes, or they could be used as note markers for when the ondes is played by string.
While the right hand is on string duty, the left hand operates a control button that determines volume, similar to the theremin. When the button isn’t pressed at all, the ondes makes no sound. The harder the button is pressed, the louder the sound, and the manner in which you press the button determines the attack of the note.
5. Stepper Motors
What are we going to do with all those old floppy drives, dot matrix printers, and other stepper motor gadgets? Why, turn them into musical instruments, of course! Those annoying sounds that we used to complain about can actually be put to good use creating musical tones.
A stepper motor rotates a gear when voltage is applied to it. These motors tend to vibrate a lot, and as we previously established, a vibrating object projects sound waves through the air. With the right software and interface device, you can control the frequency at which a stepper motor “steps” – which will determine the pitch of the sound – as well as how long it steps to determine how long a given note is played.
The result? Classic midi songs rendered on obsolete hardware.
Leave a comment letting us know what your favorite technological instruments are, and link us to some videos of great techno-performances!
(We eagerly await the ten different videos of the Imperial March played on floppy drives that everyone’s seen, but how about some more obscure examples, like Eye on the Tiger on a dot matrix printer?)
