3.2 Oscillators, filters, and envelopes
3 min read•july 22, 2024
Oscillators and waveforms are the building blocks of electronic sound synthesis. Different waveforms produce unique timbres, from pure sine waves to harmonically rich sawtooth and square waves. Understanding these shapes helps create diverse sounds in electronic music.
Filters and envelopes shape and sculpt synthesized sounds over time. Filters remove or emphasize specific frequencies, while envelopes control how parameters change. Combining these elements allows for endless sonic possibilities, from punchy basses to evolving pads.
Oscillators and Waveforms
Oscillator waveforms and harmonics
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- Sine wave generates the purest waveform containing only the fundamental frequency without additional harmonics
- Square wave contains the fundamental frequency and odd harmonics producing a bright, hollow, and buzzy sound (clarinet)
- Sawtooth wave contains the fundamental frequency and all harmonics creating a rich, bright, and buzzy sound (brass instruments)
- Harmonics in both square and sawtooth waves decrease in amplitude as they increase in frequency following a relationship
- Triangle wave contains the fundamental frequency and odd harmonics resulting in a mellow, flute-like sound
- Harmonics decrease in amplitude more rapidly than square waves following a relationship
- Pulse wave resembles a square wave but features an adjustable pulse width
- Pulse width modulation () alters the harmonic content and timbre (reed organs)
Filters and Envelopes
Filters in subtractive synthesis
- (LPF) allows frequencies below the to pass through while attenuating frequencies above it creating a darker, muffled sound (bass instruments)
- (HPF) allows frequencies above the cutoff frequency to pass through while attenuating frequencies below it producing a thinner, brighter sound (hi-hats)
- (BPF) allows a specific range of frequencies around the center frequency to pass through while attenuating frequencies outside the specified range creating a focused, narrow sound (wah-wah effect)
- (Q) emphasizes frequencies around the cutoff frequency
- Higher resonance values create a more pronounced peak at the cutoff frequency (TB-303 acid bass)
Envelope generators for parameter control
- (, , , ) envelope shapes sound over time
- Attack: time taken for the envelope to reach its maximum level (percussive vs. slow attack)
- Decay: time taken for the envelope to fall from the maximum level to the sustain level (short decay for plucks, longer for pads)
- Sustain: level maintained while the key is held down (high sustain for organ sounds, low for piano)
- Release: time taken for the envelope to fall from the sustain level to zero when the key is released (short release for staccato, longer for ambient tails)
- controls the volume of the sound over time shaping the overall dynamics (piano vs. strings)
- modulates the cutoff frequency of the filter over time creating time-varying timbral changes (filter sweeps)
- Envelopes can be applied to other parameters such as pitch or modulation depth (pitch envelopes for drum sounds)
Combining elements for synth patches
- Layer multiple oscillators with different waveforms and tunings to create complex timbres and rich, evolving sounds (detuned sawtooth waves for thick leads)
- Adjust filter settings and modulate them with envelopes to create time-varying timbral changes (filter plucks and sweeps)
- Use different envelope settings for amplitude and filter to shape the overall dynamics and timbral evolution (short amp envelope with long filter envelope for punchy basses)
- Modulate oscillator pitch with envelopes or LFOs to create pitch variations (vibrato for string patches, pitch slides for sound effects)
- Experiment with different filter types and resonance settings to explore a wide range of timbres from smooth and mellow to bright and aggressive (low-pass with high resonance for acid basses, band-pass with medium resonance for vowel-like sounds)
Key Terms to Review (26)
ADSR: ADSR stands for Attack, Decay, Sustain, and Release, which are the four stages of an envelope that shape how a sound evolves over time. This envelope controls the amplitude of a sound and significantly influences its timbre and expressiveness. By adjusting each stage of the ADSR envelope, musicians can create various dynamic sounds, enhancing the emotional impact of their music.
Amplitude Envelope: The amplitude envelope is a representation of how the loudness of a sound changes over time, typically visualized in four stages: attack, decay, sustain, and release. This envelope shapes the sound by determining its overall volume profile during its lifespan, impacting how it is perceived and interacted with in music production. Understanding the amplitude envelope is essential for creating dynamic and expressive sounds, as it interacts closely with oscillators and filters to define the sonic character of an audio signal.
Attack: In music production, attack refers to the initial phase of a sound's envelope, specifically the speed at which the sound reaches its peak level after being triggered. The attack time influences how a sound is perceived in terms of its immediacy and character, affecting everything from the punchiness of a drum hit to the articulation of a synth note. A quick attack can create a sharp and defined sound, while a slower attack can result in a more gradual onset that softens the impact.
Band-pass filter: A band-pass filter is an electronic filter that allows signals within a specific frequency range to pass through while attenuating frequencies outside that range. This filtering process is crucial in sound synthesis and manipulation, as it helps shape the tonal qualities of a sound by emphasizing certain frequency bands and reducing others, which connects directly to subtractive synthesis techniques, oscillator and filter interactions, and both analog and digital signal processing.
Chorus effect: The chorus effect is an audio processing technique that creates a richer, fuller sound by simulating the slight variations in pitch and timing that occur when multiple instruments or voices play the same note. It works by layering delayed and modulated copies of the original sound, which enhances the stereo image and adds depth to the audio signal, making it a popular choice in music production for creating a sense of spaciousness.
Cutoff frequency: Cutoff frequency refers to the specific frequency at which a filter begins to attenuate the amplitude of a signal. It serves as a critical parameter in shaping sound in synthesis, particularly in subtractive synthesis, where it defines the boundary between frequencies that are allowed to pass through a filter and those that are reduced or eliminated. Understanding cutoff frequency is essential for manipulating the tonal quality of sounds, as it directly impacts how oscillators generate harmonics and how envelopes control the behavior of these frequencies over time.
Cv/gate: CV/gate refers to control voltage and gate signals used in electronic music to control synthesizers and other equipment. Control voltage (CV) is an electrical signal that conveys information such as pitch or modulation, while gate signals are used to trigger events like note on/off actions. These elements allow for complex musical sequences and interactions between various devices, contributing significantly to the functionality of oscillators, filters, and envelopes.
Decay: In sound synthesis, decay refers to the phase of a sound's envelope where the amplitude decreases after the initial peak, shaping the sound's overall character. This reduction in volume is a crucial element in crafting a sound's dynamics and can influence the emotional impact of music. Decay is often linked with how oscillators produce tones, how filters shape frequencies, and how envelopes control the dynamics of sounds over time.
Filter envelope: A filter envelope is a modulation tool used in synthesizers to shape the frequency response of a sound over time, typically utilizing an envelope generator. It affects how the filter's cutoff frequency changes in response to the dynamics of the input signal, allowing for expressive and evolving timbres. This modulation enhances the creative possibilities when designing sounds by emphasizing or de-emphasizing certain frequencies as the sound evolves.
Flanger effect: The flanger effect is an audio processing technique that creates a sweeping, jet-like sound by combining a direct audio signal with a delayed version of itself. This effect relies on modulation to change the delay time dynamically, creating a series of peaks and troughs in the frequency spectrum, which results in a characteristic whooshing sound. It is often used in music production to add depth and movement to sounds, making it an essential tool in modern electronic music.
High-pass filter: A high-pass filter is an audio processing tool that allows signals with a frequency higher than a certain cutoff frequency to pass through while attenuating (reducing) the amplitude of frequencies lower than the cutoff. This makes it essential in shaping sound by removing unwanted low-frequency noise and enhancing clarity, especially in the context of synthesis, sampling, and mixing.
LFO Modulation: LFO modulation refers to the use of a Low-Frequency Oscillator (LFO) to create variations in different parameters of sound, such as pitch, filter cutoff, and amplitude. This technique adds movement and complexity to sounds by modulating various aspects of synthesis, enhancing expressiveness and depth. By employing LFO modulation, electronic musicians can create dynamic textures that evolve over time, making their compositions more engaging.
Low-pass filter: A low-pass filter is an audio processing tool that allows frequencies below a certain cutoff frequency to pass through while attenuating (reducing) higher frequencies. This technique is essential in shaping sound by removing unwanted high-frequency content, thus allowing for smoother, warmer tones and creating depth in the mix.
Midi cc: MIDI CC, or MIDI Continuous Controller, refers to a set of messages used in the MIDI protocol to convey real-time control information for various parameters in electronic music. This includes adjusting elements like volume, pan, effects, and other characteristics of sound generated by synthesizers, samplers, and digital audio workstations. By using MIDI CC, musicians can manipulate sounds dynamically during performance or recording.
Moog Minimoog: The Moog Minimoog is a monophonic analog synthesizer developed by Moog Music in the early 1970s, known for its rich, warm sound and user-friendly interface. It was one of the first portable synthesizers that brought complex sounds within reach of musicians, featuring a combination of oscillators, filters, and envelopes to shape audio signals, making it a staple in electronic music composition.
Pulse wave oscillator: A pulse wave oscillator is a type of waveform generator that produces a signal characterized by its sharp transitions between high and low states, creating a square-like waveform. This waveform is commonly used in synthesizers to create sounds with a rich harmonic content, and it serves as a fundamental building block in sound synthesis, connecting to other essential elements like filters and envelopes for shaping the final sound output.
PWM: PWM, or Pulse Width Modulation, is a technique used to control the amount of power delivered to an electronic device by varying the width of the pulses in a signal. This method is widely utilized in synthesizers and other electronic music instruments to modulate parameters like amplitude, filter cutoff frequency, and more. By adjusting the duty cycle of the pulse train, PWM can create a range of timbres and dynamics, making it an essential concept for sound design and synthesis.
Release: In music production, release refers to the time it takes for a sound to fade away after the note has been played or the trigger has stopped. It plays a critical role in shaping the overall character of sounds, influencing how they feel and interact with other elements in a mix.
Resonance: Resonance is the phenomenon where an object or system amplifies certain frequencies due to its natural vibrational modes. This concept is fundamental in sound and music production, as it influences how sounds are shaped and perceived. It plays a crucial role in defining timbre, enhancing specific frequencies in oscillators, and creating rich textures in synthesis methods and mixing techniques.
Roland TB-303: The Roland TB-303 is a bass synthesizer released in the early 1980s, renowned for its distinctive sound and ability to create rich, squelchy basslines. It features a unique combination of oscillators, filters, and envelopes that allow users to sculpt sounds in ways that define genres like acid house and techno. Its sequencer enables the creation of rhythmic patterns, making it a pivotal instrument in electronic music production.
Sawtooth wave oscillator: A sawtooth wave oscillator is an electronic device that generates a waveform characterized by a linear rise in amplitude followed by a sharp drop, resembling the teeth of a saw. This waveform is widely used in music synthesis for its rich harmonic content and unique timbral qualities, making it ideal for creating various sounds in electronic music production.
Sine wave oscillator: A sine wave oscillator is an electronic circuit that generates a continuous, pure tone signal characterized by a smooth, periodic oscillation resembling the shape of a sine wave. This fundamental waveform is vital in sound synthesis and is often used as a building block in more complex oscillators, filters, and envelopes to create and manipulate audio signals.
Square Wave Oscillator: A square wave oscillator is an electronic circuit that generates a square wave signal, characterized by its abrupt transitions between high and low voltage levels. This type of oscillator produces a waveform that is often used in sound synthesis, modulation, and as a basic building block for more complex waveforms. The distinct harmonic content of the square wave makes it valuable in shaping timbres in electronic music.
Subtractive synthesis: Subtractive synthesis is a sound synthesis technique that starts with a rich, harmonically complex waveform and shapes the sound by removing (or subtracting) certain frequencies using filters. This approach allows for the creation of a wide range of sounds by altering the harmonic content, which is fundamental to electronic music production and sound design.
Sustain: Sustain refers to the duration a sound maintains its presence after being initiated, particularly in electronic music. This concept is crucial as it affects how notes are perceived over time, influencing the character of melodies and harmonies. It can determine how long a sound lasts before fading away or being cut off, thus shaping the overall texture and emotional impact of a composition.
Triangle wave oscillator: A triangle wave oscillator is a type of electronic oscillator that generates a periodic waveform with a triangular shape, characterized by its linear rise and fall times. This waveform is known for its distinctive harmonic content, which includes a fundamental frequency and odd harmonics, making it an essential building block in sound synthesis and modulation techniques.