Understanding Sound Synthesis: A Beginner’s Guide

The process of creating sounds using synthesizers is called synthesis. In electronic music, synthesis is how producers transform raw electronic signals into musical sounds that we hear through loudspeakers or headphones. It all starts with sound waves generated by oscillators, which form the foundation of a synthesizer’s output. By carefully shaping these electronic signals, synthesizers create the signature tones and textures that define genres like techno, house, and ambient.

At its core, synthesis is all about shaping those signals. Whether you’re diving into subtractive, additive, or FM synthesis, the key steps—starting with a basic waveform, shaping it with filters and envelopes, adding movement with LFOs, and applying effects—are universal. This guide breaks down these steps into easy-to-follow principles, helping you understand the essential building blocks that turn raw oscillations into expressive, captivating sounds. 

The Building Blocks of Synthesis: Oscillators and Amplifiers

At the core of any synthesizer are oscillators, which generate raw sound waves that form the basis of your tone. Think of oscillators as the engine of your synth: they create waveforms like sine, square, sawtooth, and triangle waves, each with unique characteristics. For example, a sawtooth wave produces a sharp, harmonically rich sound that’s great for lead sounds, while a sine wave delivers a smooth, pure tone, perfect for creating deep basses or gentle pads. These different waveform types are what allow synthesizers to create a wide variety of sounds.

However, raw waveforms by themselves lack musicality—they need to be shaped and controlled to become more expressive. This is where the synthesizer’s signal chain comes in, specifically with amplifiers and filters. Amplifiers regulate the volume of your sound over time, adding depth and dynamics, while filters sculpt the tone by cutting out certain frequencies. By processing and layering these oscillator outputs, you can transform basic tones into complex, evolving sounds, making oscillators and amplifiers the essential building blocks of sound synthesis.

This setup allows producers to manipulate frequencies and volumes in creative ways, crafting anything from punchy leads to ambient textures. Whether you’re working on techno, ambient, or any electronic genre, understanding how to shape these fundamental building blocks can open up a world of sound design possibilities.

The Essential Signal Chain in Synthesizers

Synthesizers shape sound by passing it through a signal chain—a series of core components, each playing a vital role in crafting the final sound. The journey of a sound in a typical synthesizer follows this path:

1. Oscillator: The sound starts here, where the oscillator generates the raw waveform—whether a sine, sawtooth, square, or triangle wave. Each waveform has its unique tonal qualities, forming the building blocks of the sound.
2. Filter: This is the sculptor of your sound’s tone. Filters emphasise or remove specific frequencies, dramatically affecting the sound’s character. High-pass filters allow only higher frequencies, creating bright, airy sounds, while low-pass filters emphasise bassy tones by letting through lower frequencies.
3. Amplifier: The amplifier then controls the amplitude (volume) of the sound, allowing you to modulate loudness over time and add dynamics, making the sound more expressive and responsive.
4. Effects: Finally, effects like reverb, delay, and chorus add depth, polish, and atmosphere. Effects transform a simple tone into a full, engaging sound, providing the final touches that make it shine in a mix.

Mastering the signal chain gives you creative control over the final sound, allowing you to craft everything from sharp leads to lush pads. It’s the foundation of sound synthesis, helping you shape the unique sonic character of each sound.

Understanding (ADSR) Envelopes in Sound Synthesis

In sound synthesis, envelopes define how a sound behaves over time, adding movement and expression. Instead of a sound playing at full intensity from start to finish, envelopes allow it to evolve, responding naturally to the way it’s played—like a piano note that fades after being struck. Envelopes are defined by ADSR (Attack, Decay, Sustain, Release), each setting a unique phase in a sound’s life cycle:

• Attack (A): Determines how quickly the sound reaches its peak volume after the note is played.
• Decay (D): Defines the time it takes to drop to the sustain level after the initial peak.
• Sustain (S): The volume level held as long as the key is pressed.
• Release (R): Controls how long it takes for the sound to fade out after the key is released.

Different envelope shapes suit various sounds and playing styles:

1. Piano-Style Envelope: A quick attack, short decay, medium sustain, and short release. This shape is ideal for keys and plucked sounds, providing a natural, responsive sound.
2. Drone/Atmosphere Envelope: With a long attack, maximum sustain, and extended release, this shape is perfect for pads, atmospheres, and textures that evolve slowly over time.
3. Pluck Envelope: Features an instant attack and no sustain, with the decay setting the sound’s length. This shape is suited for bass plucks and percussive elements, giving them a sharp, distinct sound.

Understanding envelopes helps you give life and movement to static tones, transforming basic sounds into expressive, nuanced elements that fit your track’s needs.

Filtering: Shaping Your Sound’s Tone

Filters are the tone shapers in synthesis. They control which frequencies pass through, fundamentally altering your sound’s character or timbre. This is key in crafting sounds that fit into different musical contexts, whether you’re after a warm, muted tone or something sharp and biting. Here are the main types of filters:

• Low-Pass Filter (LPF): Allows only low frequencies to pass, cutting out higher ones to create a darker, bass-heavy sound. This filter type is widely used in creating warm pads or bass sounds.
• High-Pass Filter (HPF): Removes low frequencies, keeping only the higher ones, resulting in a bright, airy tone. HPFs are perfect for adding clarity to leads and high-end textures.

Many synthesizers also feature filter envelopes—envelopes that control how the filter opens and closes over time. This creates dynamic, evolving tones and is behind many classic electronic effects like sweeps and rises that add anticipation and energy to tracks.

Adding Movement with LFOs (Low-Frequency Oscillators)

While oscillators create the main sound, Low-Frequency Oscillators (LFOs) add movement and variation to it. Unlike standard oscillators, LFOs operate at slower speeds, perfect for creating rhythmic effects or organic textures instead of audible tones. By assigning an LFO to a particular parameter—such as filter cutoff, pitch, or volume—you can bring your sound to life with subtle to dramatic modulation. LFOs are essential for:

• Filter Sweeps: Link an LFO to a filter’s cutoff frequency to create a slow, evolving texture.
• Tremolo: Modulate volume to produce rhythmic pulsing, ideal for pads or leads in electronic genres.
• Vibrato: Apply LFO modulation to pitch to add musical pitch variation, creating a more expressive sound.

LFOs add that extra bit of animation to your synth patches, making them feel less robotic and more engaging. By experimenting with different modulation rates and depths, you can craft evolving sounds that keep listeners hooked.

Read more: What is a LFO? Mastering Low-Frequency Oscillators