Synthesizer Basics: Amplitude, Oscillators, Timbre | Music Production | Berklee Online

Synthesizer Basics: Amplitude, Oscillators, Timbre | Music Production | Berklee Online

[MUSIC PLAYING] Amplitude. When you’re looking at a two
dimensional waveform display, amplitude is the height
of that waveform. For audio signals, this equates
to the sounds of loudness. A quiet sound, like a whisper,
will have a small amplitude, while a sound with a lot of energy like
a jet engine has a larger amplitude. A good metaphor for
amplitude is altitude. We measure the height
of mountains as being a certain number of feet above sea
level and the depths and valleys of the oceans to be below sea level. Just like sound, mountains can be
formed by two elements colliding. For sound, it might be a finger
plucking a string or striking a key. And in regards to mountains,
it would be two tectonic plates running into each other. Depending on how much energy
is behind these collisions, the resulting sound will have
a varying degree of loudness, which is equivalent to its amplitude. In a way, you can visualize a
mountain’s amplitude just by looking up. Imagine how loud that
collision must have been. The word envelope is the one that
pops up a whole lot in sound design and can be challenging to visualize. Think of the word
envelope in its noun form. It’s what you put a letter inside
of to send away in the mail. It’s a thing that is. But since music is a thing
that is happening or happens, it’s more useful to think of
the word in its verb form– to envelop. The definition of envelop is to
completely enclose or surround, which is exactly what an envelope does. A paper envelope encloses a letter. And very much in the same way, the
envelopes on a synthesizer or effect take an audio signal and
wrap themselves around it, shaping and carving the sound from
the moment it begins until it ends. Similar to how a filter
shapes the timbre of a sound, an envelope shapes the
evolution of a sound. The most common envelope
you’ll see is an amp envelope, which shapes amplitude over time. But there are many other possibilities. Another common use of an
envelope is to wrap itself around a sound’s brightness. Frequency is a word that
you’ll see time and time again. Frequency is how often something
occurs in a specified amount of time. To put it in context of your life, think
about how frequently you eat per day. Three times? Your meal frequency is
three meals per day. Or think about how frequently
your heart is beating. It typically varies between
60 to 180 beats per minute, depending on whether you’re resting
or exerting a lot of energy. In the context of music
production, frequency refers to how often a
waveform repeats each second and is measured in an
increment of Hertz. One Hertz means once per second. If something is vibrating at 20 Hertz,
it is repeating 20 times each second and produces a very low pitch. If an oscillator is vibrating at
16,000 Hertz, it’s moving a lot faster and produces a much higher pitch. So frequency not only relates
to how often something occurs, but in our world, it also
relates to the pitch of a note. A good metaphor for
frequency is a car engine. As you put your foot on the
gas, the engine spins faster. And as that frequency of
revolutions per minute increases, so does the speed of the car. As this is happening, you can literally
hear the resulting rise in pitch. Regular car engines are usually
cruising between 2,000 to 3,000 RPM, which results in an exhaust
pitch somewhere between 30 to 50 Hertz, which is in the lowest
octaves that humans can hear. Formula One cars rotate considerably
faster, resulting in a pitch around 1,200 Hertz, which
is around an E flat six. To reiterate, frequency is a measure
of how fast a waveform vibrates, which is directly related
to its subsequent pitch. Both of these ideas are important
to keep in mind as you adjust the frequency parameter on any device. Oscillators are the part of your
synthesizers that create sound. Think of them as throats. They produce electronic signal which
creates a vibration that oscillates back and forth just like vocal chords. Oscillators use specific voices to sing
with and emit wave forms, such as sine, square, saw, and triangle– each with their own distinctive timbre. Some synthesizers only
have a single oscillator. But others have several
which can all sing at the same time, each with
their own pitch or tone, creating layered and
multi-timbral sounds. Filters are everywhere. They’re in our water pitchers,
our air conditioners, and our social media
apps, just to name a few. We encounter them so often that
they’re almost like background noise. Speaking of background noise,
we could use an audio filter to get rid of some of that. Let’s correlate an audio
filter to a kitchen strainer. We pour a pot of pasta
into a strainer, which separates the liquid from the solids. In our case, we’re sending
audio into a filter, which is only allowing certain
frequencies to pass through it, separating the ones we want
from those that we don’t. But as you might expect,
filters are a bit more elaborate than kitchen strainers. Not only can we completely separate
out frequencies we do not want, but we can also choose to
only reduce their amplitude or increase them, allowing us to sculpt
and shape the timbre of our sounds. Oscillators tend to
emit very bright sounds. So often, you’ll see a
low pass filter used, which is allowing the low frequencies
to pass through the filter and reach your ears
while eliminating some of the higher more harsh frequencies. Another word for timbre is tone. Timbre is the distinguishing
characteristic that differentiates one sound
from another, despite the fact that they might be playing the same
frequency with the same amplitude. When we’re describing
a sound’s timbre, we use words like sharp, round, reedy,
brassy, or bright to describe them. Let’s correlate timbre to flavor. Think of apples. They’re a type of fruit that has a
typical shape, color, and flavor. But inside the category of apples,
there’s a huge amount of variation. Some apples are very sweet,
while others are more sour. Some are red, while others are green. They’re all still apples, but each
one with a distinct characteristic. Red Delicious is different from
McIntosh is different from Gala is different from Honeycrisp. Even when describing one type,
there might be variations from apple to apple. Same thing goes for sound sources. One category of timbre we
use quite often is strings. Inside of the string family, we
have violins, violas, cellos, and double basses. They have similar timbres and tones in
some ways, but each one is distinct. When comparing two
different violins, one might have a very bright sound, while
the other is more muted and dark. Even when playing one violin,
we can produce different timbres by bowing a different way. LFO stands for low frequency oscillator
and is exactly what the name suggests. It’s an oscillator which emits
an electronic signal just like any oscillator, but its signal
is at a very, very low frequency. So low, in fact, that it’s often
below the range of human hearing. You might ask yourself, why would
someone create an oscillator which emits a sound we can’t hear? Well, the answer goes back
to the idea of vibrations. The waveform an oscillator creates
travels back and forth, back and forth, back and forth, like a pendulum. And we can use that movement to
create a lot of musical effects. An LFO swings back and
forth, but outputs a signal that is not coloring the sound. Instead, we use that oscillation
to control other parameters. Many common effects
are created with LFOs. If we assign the LFO’s pendulum swing
to a volume knob, we have a tremolo– a repeating change in amplitude. If we assign it to a frequency
parameter, we get vibrato– a repeating change of pitch patterns. When we assign it to the cutoff
frequency parameter of a filter, we get a cyclic variation
in timbre, which is how we get those cool wobble bass lines. Modulation is change. It’s a word you’ve probably
heard when referring to a key change that occurs mid-song. Think of Beyonce’s
Love On Top, which has four modulations towards the end
of the song, each time raising the harmonic root a half step up,
creating a harmonic ascending line cliche. In this case, modulation is referring
to change of harmony or key center. In all the devices you
load into Live, modulation can relate to pretty much any parameters
since they can all be changed. To tie two concepts together now, the
most useful modulation of an oscillator is pitch, which is assigned to
the keys on a keyboard, also known as key tracking. In the same way that Love On
Top is moving in half steps, as we move up the keyboard
note by note, we’re modulating the pitch of an
oscillator by a half step each time. An LFO uses its oscillator as a control
signal to modulate other parameters. To go back to our previous examples,
in order to create tremolo, we modulate volume at a
certain rate or frequency. To create vibrato, we modulate pitch. And to create a wobble bass, we
modulate frequency cut off of a filter.


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