Explain the usage of the 5 most important synthesis modules:

Oscillator, Filter, Amplifier, Envelope, and LFO.

Objectives

To understand the usage of the 5 most

important synthesis modules:-

Oscillator

Filter

Amplifier

Envelope

LFO

My name is Subrina, originally from Singapore but currently

residing in Seattle, Washington State, USA. I decided to teach

this topic as I always feel that with every subject, understanding

the basics is crucial. Similarly in music production, it is essential to

understand the 5 most important synthesis modules before attempting

to manipulate these when working with the DAW.

5 most important synthesis modules

Before we explore the 5 most important synthesis modules, let us first

look at an overview of subtractive synthesizer components:-

Oscillator

What is an oscillator?

An oscillator generates the basic signal. This is usually a waveform that is rich in harmonics. Many synthesizers offer more than one oscillator.

Will either be labeled as “osc” or oscillator.

The audio signal of a synthesizer is generated by the oscillator. Usually you would choose from a selection of waveforms that contain differing types and varying amounts (more or fewer) of harmonics. The level relationships between the fundamental tone and the harmonics of the chosen waveform are responsible for the basic sound color or timbre.

Oscillator

Common synthesizer waveforms and their

characteristics are:-

Sine Wave: Clean and clear-sounding, a sine wave contains no harmonics but the first harmonic; in other words, it is the fundamental tone. The sine wave—used standalone—can be used to create “pure” sounds like whistles, the sound of wet fingers on the rim of a glass, tuning forks, and so on.

Oscillator

Sawtooth: Clear and bright-sounding, a sawtooth wave contains both odd and even harmonics. It is ideal for the creation of string, pad, bass, and brass sounds.

Oscillator Square and Pulse Waves: Hollow and woody-sounding, a square

wave can contain a wide range of odd harmonics. It is useful when creating reed instruments, pads, and basses. It can also be used to emulate kick drums, congas, tom-toms, and other percussive instruments—often blended with another oscillator waveform, such as noise.

Oscillator

The square wave can be reshaped to make the waveform cycles—or pulses—more rectangular on many synthesizers, using a pulse width modulation (PWM) control. The more rectangular the wave becomes, the more nasal it sounds. When modulated in this way, the square wave is known as a pulse wave, and contains fewer harmonics. It can be used for reeds, basses, and brass sounds.

Oscillator

Triangle: Like a square wave, a triangle wave contains only odd harmonics. Because a triangle wave’s higher harmonics roll off faster than the ones of a square wave, the triangle wave sounds softer. It is ideal for creating flute sounds, pads, and vocal “oohs.”

Oscillator

Noise: Pink/Red, Blue, White: Noise is useful for emulating percussive sounds, such as snare drums, or wind and surf sounds, among others.

-White noise: The most common noise waveform found on synthesizers. White noise contains all frequencies—at full level—around a center frequency.

Oscillator-Pink and red noise: These noise colors also contain all frequencies, but they are not at full level across the frequency spectrum. Pink noisedecreases the level by 3 dB per octave (of higher frequencies). Red noise decreases the level by 6 dB per octave.

-Blue noise: Blue noise, which is the reverse of pink noise, increases the level of all frequencies in higher octaves by 3 dB.

FilterWhat is the filter and what is its purpose? Used to alter the basic signal by filtering out (removing) portions of the

frequency spectrum. Many synthesizers offer a single filter, which is applied universally to all oscillator signals. Multioscillator synthesizers can provide multiple filters, allowing each oscillator signal to be filtered in a different way.

The purpose of the filter in a subtractive synthesizer is to remove portions of the signal—the frequency spectrum—that is sent from the oscillators. After being filtered, a brilliant-sounding sawtooth wave can become a smooth, warm sound without sharp treble.

The filter sections of most subtractive synthesizers contain two primary controls known as cutoff frequency—often simply called cutoff—and resonance. Other filter parameters can include drive and slope. The filter section of most synthesizers can be modulated by envelopes, LFOs, the keyboard, or other controls such as the modulation wheel.

FilterTypes of filters:-

There are several filter types. Each has a different effect on various

portions of the frequency spectrum: Lowpass filter: Low frequencies are passed; high frequencies are attenuated. Highpass filter: High frequencies are passed; low frequencies are attenuated. Bandpass filter: Only frequencies within a frequency band are passed. Band Reject filter: Only frequencies within a frequency band are attenuated. Allpass filter: All frequencies in the spectrum are passed, but the phase of the output is modified

Filter

Cutoff Frequency: The cutoff frequency, or cutoff, as the name suggests, determines where the signal is cut off. Simpler synthesizers offer only lowpass filters. Thus, if a signal contains frequencies that range from 20 to 4000 Hz, and a cutoff frequency is set at 2500 Hz, frequencies above 2500 Hz are filtered. The lowpass filter allows frequencies below the cutoff point of 2500 Hz to pass through, unaffected.

Filter

The figure below shows an overview of a sawtooth wave (A = 220 Hz).

The filter is open, with cutoff set to its maximum value. In other words,

this waveform is not being filtered.

FilterThe figure below shows a sawtooth wave with the filter cutoff set to

about a 50% value. This filter setting results in suppression of the

higher frequencies and a rounding of the edges of the sawtooth wave,

making it resemble a sine wave. Sonically, this setting makes the sound

Much softer and less brassy.

From this example, we can see that use of the filters to cut away

portions of the frequency spectrum alters the waveform’s shape, thus

changing the timbre of the sound.

Amplifier

What is the amplifier?

Amplifier : Used to control the level of the signal over time. The amplifier features a module known as an envelope, which is broken down into several elements that provide level control for the beginning, middle, and end portions of your sound. Simple synthesizers generally offer a single envelope, which is used to control the oscillator (and filter) over time. More complex synthesizers can feature multiple envelopes.

Envelope The amplifier module of a synthesizer is responsible for controlling

the level—or loudness—of the signal over time.

To put this into a musical context, consider the sound of a violin, which slowly ramps up to a peak—or maximum—level as the bow is smoothly dragged across a string, is sustained for a period until the bow is moved away from the string, and then cuts off abruptly. In comparison, hitting a snare drum with a drumstick results in a very fast peak level, with no sustain portion, and the sound immediately dies out (although there will be an amount of decay, the time it takes to fall from the peak level). As you can see, these two sounds have very different characteristics over time.

Synthesizers emulate these sonic characteristics by providing control over different parts—the beginning, middle, and end—of a sound’s level over time. This control is achieved with a component called an envelope generator.

Envelope The Attack, Decay, Sustain, and Release (ADSR) Envelope Controls:

An oscillogram of a percussive tone is shown below in which the level rises immediately to the top of its range and then decays. If you drew a box around the upper half of the oscillogram, you could consider it the “envelope” of the sound—an image of the level as a function of time. It is the function of the envelope generator to set the shape of this envelope.

EnvelopeThe envelope generator usually features four controls—attack, decay,sustain and release, commonly abbreviated as ADSR.

Attack: Controls the time it takes for the initial slide from an amplitude of zero to 100% (full amplitude).

Decay: Determines the time taken for the subsequent fall from 100% amplitude to the designated sustain level.

Sustain: Sets the steady amplitude level produced when a key is held down.

Release: Sets the time it takes for the sound to decay from the sustain level to an amplitude of zero when the key is released.

If a key is released during the attack or decay stage, the sustain phase isusually skipped. A sustain level of zero will produce a piano-like—orpercussive—envelope, with no continuous steady level, even when a key isheld.

LFOWhat is LFO? A low frequency oscillator, or LFO, is an oscillator designed to

produce signals whose frequency is at the bottom of, or below, the audio range. Nearly all synthesizers have at least one LFO or a digital equivalent. It is useful for producing a repeating control signal for a wide variety of purposes; when added to the control input of a VCO it produces the effect known as vibrato, and if it is added to the control signal of a VCA, it produces tremolo. A typical LFO can generate variety of useful waveforms including sine, triangle, square, ramp-up, and ramp down. The most useful LFOs have an upper frequency limit above 100 Hz and a lower limit below 1 Hz (such frequencies may be given as seconds/cycle; for instance, a frequency of 20 seconds/cycle corresponds to 0.05 Hz). An LFO may or may not have voltage control over its frequency or other wave parameters; an LFO with voltage control over the frequency is sometimes referred to as a "VCLFO".

Thank you for taking the time to read through

the contents of my presentation. I certainly

hope you have learnt as much as I have and that

you will utilize information here for your future

music projects. Good luck!