Synthesizers are the most modest
musical instruments you can imagine. They look like small and rather mundane
electronic pianos, but they're actually much more than that. If you can
play a synthesizer, you can play not just any instrument in the
orchestra but any instrument you could possibly imagine! Synthesizers
have radically changed popular music since they were first widely
used in the early 1970s; hardly a pop record is made these days
without featuring an electronic keyboard of some kind. How do these
amazing gadgets work? Let's take a closer look!
Photo: Two in one: There are two completely separate electronic synthesizer keyboards stacked together here. The top one is a 61-key Yamaha Motif ES 6; underneath there's a Kurzweil. Unlike a piano, the sounds from these keyboards can be changed in all kinds of ways
using the switches and knobs at the top. A small digital display (green, center) helps you program the machine. Photo by Edward G. Martens
courtesy of US Navy.
What is a synthesizer?
Photo: The Yamaha DX-9 synthesizer, popular in the 1980s, is much more than just an electronic piano! Other famous makes of synthesizers include Moog, Roland, Korg, and Casio.
A synthesizer (sometimes spelled "synthesiser") is an
electronic keyboard that can
generate or copy virtually any kind of sound, making it able to mimic
the sound of a traditional instrument, such as a violin or piano, or
create brand new, undreamed of sounds—like the crunch of footsteps
on the surface of Mars or the noise blood cells make when they tumble
through our veins. "Synthesize" means to make something new,
often by putting it together from existing pieces. So we can think of
a synthesizer as an electronic gadget that makes new sounds by
piecing together "old" ones. To understand how it does that, we
need to know more about sound and how different instruments produce
it in different ways.
Sound is energy in motion
Suppose you're sitting in a room with a friend who
has a large drum that she bangs from time to time with a large
stick so, every so often, you hear a drum beat. What sort of science
is going on here? Playing and hearing the drum actually involves a
series of steps in which energy is converted
from one from to
Photo: A marching drummer is firing sound energy off in all directions.
Photo of drummers from from the Royal Australian Navy by William R. Goodwin
courtesy of US Navy.
When your friend lifts her drum-stick, she gives
her arm (and the stick) potential energy
(the ability to do
something). When she lowers her arm, moving it back toward the drum
at some speed, it has kinetic energy (the
energy something has
because it's moving). As the drum stick contacts the taut drum skin,
soaks up most of the energy and starts to vibrate. In other words, it
has the kinetic energy now. As the skin vibrates, it pushes the air
molecules that are in contact with it. The air molecules vibrate too,
with each molecule causing neighboring molecules to start vibrating as
well. Before long, all the air molecules in the room are vibrating.
Some of them vibrate right next to your ear; others vibrate in your
ear canal. Inside your ear, the vibrating air molecules make tiny
hairs vibrate. The hairs stimulate nerve cells, which send signals to
your brain—and your brain perceives these signals as sounds.
In short, we can think of sounds as waves of energy
traveling from something that is moving back and forth (vibrating or
oscillating) to our ears. The waves travel by alternately
squeezing and stretching the air; if there's no air in the room, they
cannot travel at all. That's why you can't hear sounds in space,
where there's no air, or traveling in a vacuum. If you could see sound
waves moving, you'd see the air squeezing and stretching all
over your room like an old-fashioned concertina. In science, the
squeezed parts of the air are known as compressions
the air molecules are pressed together) and the stretched parts are
called rarefactions (because the air
molecules are thinned out and less dense).
Two key features of a sound wave control what it
sounds like to us. The frequency (how many
times the wave
vibrates in one second) is broadly related to the pitch of the sound
we hear. So we hear a high-frequency sound as having a higher pitch.
In other words, a choir boy's voice produces a mixture of sound waves
of generally higher frequency than an adult man's voice. The
amplitude (volume) of a sound is related to the
amount of energy that the sound waves carry. When you bang a drum hard,
you make more energetic sound waves with more amplitude that you hear
as louder sounds.
What makes one instrument sound different from another?
When two instruments play exactly the same musical
note, at roughly the same volume, they can sound completely
different. How can that be if they're producing the same sound waves?
The answer should be obvious: they're not producing the same
sound waves! We can use an oscilloscope (an
electronic graph-drawing machine, a bit like a cathode-ray TV, only it shows pictures of
what waves look like) to see the difference.
Artwork: Sine, square, sawtooth, and triangular waves as they'd
appear on the screen of an oscilloscope.
If we play a pure musical note with a tuning fork,
the oscilloscope shows an undulating hilly pattern called a
sine wave. But if we play the same note with
a trumpet, the wave will look more zig-zagged, like the teeth of a saw (it's usually
called a saw-tooth wave). If we play
the same note again on a flute, we will see triangular waves,
while a clarinet, blown hard, playing exactly the same note, might well give us
The shape of the sound waves , which is controlled by how the instrument pumps energy
into the world around it—in other words, how it vibrates and makes
the air around or inside it vibrate in sympathy—is one of the
things that makes instruments sound different from one another.
You can hear the difference between sine waves, square waves, and sawtooth waves in this little sound clip.
In each case, we're hearing a note with exactly the same frequency (440 Hz):
There are other factors too. An instrument doesn't
just produce a single sound wave at a single pitch (frequency). Even
if it's playing a steady note, it's making many different sound waves at
once: it makes one note (called a fundamental
first harmonic) and lots of higher, related notes called
harmonics or overtones. Playing together, the
harmonics make a dense,
complex sound a bit like a barber's shop choir, with low voices and
high voices all singing in tune. The more harmonics
there are, the richer the sound.
A third factor that makes instruments different is
the way the sound waves they make change in volume (amplitude) over
time. Instruments don't make sounds the way lamps make light: it's
not "all" or "nothing." If you press a piano key and release
it, the sound changes volume gradually over time. First, it rises
quickly (or "attacks") to its maximum volume. Next, the sound
"decays" to a lower level and stays there or "sustains."
Finally, when we let go of the key, the sound "releases" and dies
down to silence.
In a piano, the attack phase is fairly slow and the
sustain phase can be really long as the notes take a long time to die
away. But with a flute, the attack phase is quicker and sharper,
there is little decay, the sustain continues for as long as the
flautist keeps blowing, and the release is also very fast. The
changing pattern of sound volume plays a huge part in what makes one
instrument sound different from another. We call the pattern of
attack, decay, sustain, and release the ADSR
Picture: An ADSR envelope shows how the volume of
a musical note changes with time. When a sound plays, it attacks to a
maximum volume, decays to a lower level, sustains or holds at that
level for a while, then releases back to silence.
How synthesizers work
Now we understand the theory of how sound works,
and how different instruments produce it in different ways, we know
enough to build ourselves a synthesizer. You can probably see already
that a machine that can copy the sounds of virtually any other
instrument would need to be able to:
Generate sound waves of different shapes.
Generate more than one sound tone at once to produce a fundamental frequency and harmonics.
Make the volume of the sound change over time to produce different ADSR envelope shapes.
That's pretty much what an electronic
synthesizer does in a nutshell. It has a number of different voices or
(sound tone generators), each of which can produce waves of different
shapes (sine wave, square wave, saw tooth, triangular wave, and so
on). It can combine the waves to make complex sounds, and it can vary
the way the sounds attack, decay, sustain, and release to make the
sounds mimic existing instruments like pianos.
To make a synthesizer sound somewhere between a
piano and an organ, you could select a square wave generator (which
gives an organ-like sound) and set the ADSR values to be like those
of a traditional piano (slowish attack, quickish decay, long sustain
and release). Modern synthesizers have "presets"
(ready-programmed settings) or "modes" that let you select
particular instruments at the flick of a single switch. Of course,
you don't have to copy traditional instruments with a synthesizer:
you can change the settings to whatever you like—and create all
kinds of sounds no-one has ever heard before.
Adding or subtracting?
In art, there are two ways to make a piece of sculpture. You can take materials you've found in the world
around you and stick them together to make something completely new. That would be an example of working in
an additive way. Or you can start with something like a big block of stone or wood and chisel it down, slowly reducing
it to what you want by stripping bits away. That's working in the opposite—subtractive—way.
The same is true of making sounds with synthesizers. It's perfectly possible to build up a complex sound from
simple tones that you add together and shape in various ways, which is more or less the approach I've described
above. But it's much more common for real synthesizers to work the other way, through subtractive synthesis. That means you start with a complex sound, filter it to remove harmonics, and envelope shape its volume.
In practice, then, a simple subtractive synthesizer makes sound using four independent components:
An oscillator generates the original sound (and you can control it in various ways), which will be a mixture of a fundamental frequency and its harmonics. Most synthesizers have at least a couple of oscillators.
A filter cuts out some of the harmonics (for example, by boosting or cutting all harmonics above a certain frequency).
An amplifier changes the volume of the sound over time, according to ADSR values that you set (as we discussed above).
A second, independent oscillator, known as an LFO (low-frequency oscillator), can be used to vary how the previous three stages work, producing some very interesting effects. For example, if you apply the LFO to the original oscillator, it makes the sound it generates wobble about in what's called a tremelo effect.
Yes, this is all sounds a bit abstract and mathematical. It's easiest to understand what it means in practice by experimenting for yourself; at the bottom of this article you'll find some suggestions for apps you can download that let you play around with your own simple subtractive synthesizer.
Analog and digital synthesizers
The original synthesizers achieved all this using laboratory-style electronic equipment that generated and manipulated
actual sound waves. Instruments like this are known as analog synthesizers because they work directly with the sound waves themselves. Many of these synthesizers had lots of separate,
sound-creating modules that could be connected together ("patched") in different ways; that's why they
were called modular synthesizers.
Photo: Modular Synthesizer is an iPhone app that
replicates an analog, modular synthesizer on your smartphone—even down
to the neat, old-fashioned "patch cords" (cables) that connect different
modules together. Search on "synthesizer" in your favorite app store and
you'll find all kinds of neat synthesizers you can play with, from simple
on-screen keyboards right up to authentic gadgets like this one, which can
export your tunes direct to sites like Soundcloud.
The RCA Synthesizer: Back in the 1950s, the world's first analog electronic synthesizer
was programmed using reels of paper tape, punched with holes that represented things like the frequency, octave,
envelope, and volume of the sounds required. From US Patent 2,855,816: Music synthesizer by Harry F. Olson and Herbert Belar, courtesy of US Patent and Trademark Office.
Modern synthesizers do everything
digitally, by manipulating numbers with computer chips. Not
surprisingly, they're called digital synthesizers.
essentially computers that have been specially programmed to generate
and manipulate sounds. Most synthesizers can be connected up to
personal computers, so the computer can be used to store and record
the sounds the synthesizer makes or play it automatically. To make this
sort of thing
easier, computers and synthesizers use a standard way of connecting
together known as MIDI (Musical Instrument Digital
Another kind of digital synthesizer, the sampler,
lets you feed in a
recorded sound (maybe the noise of a sparrow singing) and then
manipulate it in various ways by changing the sound settings. So you
can make the sparrow sing more quickly by speeding up the sound, or
play the bird-song on your keyboard, so the low notes sound like
older, heavier birds and the high notes like younger, smaller, and
How to make your own synthesizer using Audacity
Synthesizers sound amazingly abstract when you read about them in articles like this—and
there's really no substitute for playing with them yourself. Now you might not be able to
afford a multi-thousand dollar synthesizer, but you can download a free sound-editing program
called Audacity (for Windows,
Linux, and Mac) and experiment with quite a lot of sound-making effects without spending a dime.
The great thing about Audacity is that you can see the shapes of the waves you create
and listen to them at the same time. I'd really recommend playing around with basic sounds like this
for an hour or two before you move on to using realistic synthesizer apps. This way, you'll get a feel for how the shape of a sound corresponds to what you actually hear, which can be difficult to figure out if you just play with an app.
I'm not going to explain in detail how to use Audacity, because you can use it for many different things (from
converting cassette tapes to MP3s to creating brand new imaginary sounds). To learn about synthesizers, what you need to do is experiment with the tabs marked "Generate" (which can produce sound
wave tones of different shapes and frequencies, as well as "white noise"—sound spread equally across a wide range
of frequencies) and "Effect" (which will shape the envelopes of the tones you've generated or change them in other interesting ways). Here are three quick examples of sounds I've made to give you an idea.
1. Basic harmonics
In my first attempt at synthesizing a sound, I've added together three square waves of 110 Hz (top), 220 Hz (middle), and 440 Hz
(bottom). Then I've faded in the sound at the start (giving a slowly rising attack) and faded it out at the end (giving an even more gradual release), so there's no decay or sustain. That gives me these three fish-shaped envelopes, which are added together in the final sound; the three tones play simultaneously, but our ears add them together so we hear a single, fused sound about 0.5 seconds long:
The result sounds fairly harsh—not something I'd particularly want to listen to:
2. Adding a wah-wah effect
Next, I've taken the same three waves and applied a wah-wah effect, which wobbles the amplitude up and down to resemble a human voice. Notice how this changes the envelopes of the waveforms without changing the frequencies of the sounds. The higher frequency sounds are changed more than the lower frequency sound:
It sounds much less abrasive and a bit more interesting. With more work, we could get this quite close to a human vowel sound:
3. Adding noise
For my final example, I've reduced the amplitude of the middle tone by about 50 percent (so the peaks in the trace below are about half as high), removed the lowest tone entirely, and replaced it with white noise that attacks and decays in roughly the same time period. What I'm starting to get now is more interesting:
Here's what it sounds like—more windy and whistle-like, but still recognizably the same note (frequency). The white noise is starting to take us in a different direction; what we have now sounds like some sort of windy blowpipe:
Clearly we could go on doing this forever. We could add any number of sounds, change their frequencies, durations, wave shapes, or envelopes, and refine each component sound in many different ways. With a synthesizer, the possibilities really are infinite!
And for your next trick...
Artwork: A screenshot of Common Analog Synthesizer by oxxxide. Although it has only a puny keyboard (which you can scroll up and down for higher and lower notes), it's a surprisingly powerful demonstration of basic subtractive synthesis and a good place to go next.
Once you've mastered Audacity (or exhausted it, depending on your point of view), it's time to move on to a real synthesizer.
Assuming you haven't got access to an actual synth, nip along to your favorite app store and search for "synthesizer."
On the iPhone/iTunes store, you'll find quite a few very realistic synth apps like Modular (from Pulse Code), KORG Gadget (from KORG themselves), and Peter Vogel CMI (a faithful, mini-reproduction of the classic Fairlight CMI synthesizer from the 1980s produced by its original inventor). Over in Android land, Common Analog Synthesizer (from oxxxide) is a great place to start; very similar to the basic subtractive synthesizer I outlined above, it has two oscillators (offering a choice of sine, square, pulse, and sawtooth wave), an ADSR filter, an ADSR amplifier, an LFO, and a few other bits and pieces. If you haven't got a smartphone or tablet, don't despair; there are also various PC synthesizer programs (such as the CM101 produced a few years ago by Muon Software and now superseded by various improved models).
Who invented synthesizers?
1863: German physicist Hermann Helmholtz (1821–1894) develops the modern scientific theory of how we hear music by perceiving sound tones.
1917: Léon Thérémin (1896–1993) invents the Thérémin,
a radio-like box that makes an eerie swooping noise when you move your hand nearer to or further from its antenna. It's still widely used in horror movies to this day.
1922: Maurice Martenot (1898–1980) develops the Ondes Martenot, one of the first electronic keyboard instruments. It features in numerous 20th-century orchestral compositions, notably Oliver Messiaen's
Turangalîla Symphony (composed
1954: Harry F. Olsen (1901–1982) produces the groundbreaking RCA synthesizer.
1950s–2000s: Influential German composer Karlheinz Stockhausen (1928–2007) bridges the gap between the worlds of classical and electronic music.
1964: After experimenting with Thérémins, Robert Moog (1934–2005) develops his pioneering, affordable Moog synthesizers, ushering in the age of electronic music.
Late 1970s: Digital sampler-synthesizers such as the Fairlight CMI
and Synclavier lead to a huge increase in sampled and digitally treated
electronic music in the early 1980s.
1982: Computer scientist (and later futurologist) Ray Kurzweil (1948–) begins developing digital electronic keyboards.
1984: Different synthesizer makers agree to use the MIDI interface to provide a standard way of connecting together computers and electronic musical instruments. Yamaha's DX7 was one of the first commercially available machines to use MIDI.
1990s: Musicians and computer scientists such as Jaron Lanier (1960–) develop virtual reality instruments.
2011: Synthesizer pioneer Peter Vogel (1954–) launches an iPhone app version of his classic Fairlight CMI synthesizer from the 1980s.