What Is a Synthesizer? How Synths Make Sound, Explained

What is a synthesizer?

A synthesizer is an electronic instrument that creates sound from scratch by generating a raw waveform and then shaping it with filters, envelopes and modulation. Unlike a sampler, it does not need a recording to start from, so the same instrument can produce a sub bass, a bright lead or a slow evolving pad.

The modern synth traces back to Robert Moog's modular synthesizer from 1964, generally described as the first commercial synthesizer. Its key idea was voltage control: voltage-controlled oscillators set pitch, and voltage-controlled amplifiers set loudness^[1]. In 1970 the Minimoog squeezed that concept into a portable keyboard and became the first synthesizer sold in retail stores^[2]. Today most producers meet synths as plugins, but the building blocks have barely changed.

How does a synthesizer make sound?

A synth makes sound in a chain: an oscillator generates a harmonically rich signal, a filter removes part of its frequency spectrum, and an amplifier controlled by an envelope shapes its volume over time. Modulators such as LFOs then move those settings while the note plays.

Apple's Logic Pro guide notes that most synthesizers follow a similar architecture and signal flow based on subtractive synthesis principles, even though there are many other approaches^[3]. Its analogy is Michelangelo carving David: you cut away the parts of the sound you do not want^[3]. Learn this chain once and almost every synth interface starts to make sense.

• Oscillator Generates the basic signal, usually a waveform rich in harmonics. Many synths offer more than one oscillator and several waveform types^[4].
• Filter Removes portions of the frequency spectrum. A low-pass filter darkens the sound as you lower its cutoff, which is the move behind most filter sweeps.
• Amplifier and envelope Controls level over time. The envelope shapes the beginning, middle and end of each note, usually with attack, decay, sustain and release stages^[4].
• LFO A low frequency oscillator that modulates other parameters, for example wobbling filter cutoff or adding vibrato to pitch^[4].
• Global controls Tuning, glide between notes, pitch bend and the choice of monophonic or polyphonic playback^[4].

What do the basic synth waveforms sound like?

Each basic waveform has a fixed recipe of harmonics, and that recipe sets the starting tone before any filtering. Choosing the right wave gets you most of the way to a sound, so it is the first decision in any patch.

Apple's oscillator reference describes the four classic shapes and noise^[5]. The table sums it up with typical uses in beats.

A useful habit: start a bass on a sine or triangle when you need clean low end, and start leads on a saw when you want them to cut through a busy mix.

What are the main types of synthesizers?

Synths are grouped by how they generate tone. Subtractive, FM and wavetable cover most of what you will meet in a DAW, and the analog vs digital split describes the circuitry rather than the method.

Apple's FM reference explains that FM synths typically have no filter and excel at bell timbres, metallic tones and electric piano tines, and that the DX7, sold from 1983 to 1986, remains the most commercially successful professional-level hardware synthesizer ever made^[6]. Wavetable synthesis produces a smooth blend from one waveform into another and was championed by PPG and Waldorf^[7]. For deeper dives, see the FM synthesis beginner's guide and the wavetable synthesis explainer.

Analog vs digital synths

An analog synth generates and shapes sound with electronic circuits, while a digital synth calculates it with code or DSP chips. The Minimoog's three oscillators were never perfectly synchronized because of an unstable power supply, which is part of why its sound is described as warm^[2]. Virtual analog plugins model that behavior in software, so the difference today is mostly about workflow, cost and character rather than what is possible.

Software vs hardware synthesizers

A software synth is a plugin that runs inside your DAW, and a hardware synth is a physical instrument with its own sound engine and controls. Both read the same MIDI notes, so a melody you write in the piano roll can drive either one.

Software wins on price, recall and instance count. Hardware wins on hands-on control and on keeping your computer's CPU free. Most beginners should start in software; the hardware synth vs VST comparison covers when a physical synth is worth the money.

• Software synth Cheap or free, opens as many instances as your CPU allows, and saves every setting inside the project.
• Hardware synth Physical knobs, no CPU load for the sound engine, but recording means routing audio into an interface in real time.
• Hybrid Some companies ship plugin versions of their hardware, so patches can move between the two.

How do you program your first synth sound?

Start from an initialized patch and build a simple mono bass one module at a time, following the signal chain. The settings below are starting points to adjust by ear, not fixed rules.

1. Initialize the patch
   Load the synth's init or default preset so no hidden modulation or effects color the result.
2. Pick a sawtooth oscillator
   Use one saw, or two saws detuned by 5 to 10 cents for width. Set the octave so the bass sits around C1 to C2.
3. Set mono and glide
   Switch to monophonic playback and add a short glide, around 30 to 80 ms, so overlapping notes slide.
4. Close the low-pass filter
   Lower cutoff until the buzz softens, often somewhere between 300 Hz and 1 kHz, and keep resonance low for now.
5. Add a filter envelope
   Give the filter envelope a fast attack, 150 to 300 ms of decay and low sustain. Raise its amount until each note has a short bright pluck.
6. Shape the amp envelope
   Attack at 0 ms, sustain full, release around 50 to 100 ms so notes stop cleanly without clicking.
7. Save it and write a line
   Save the patch with a clear name, then program a two-bar bassline and tweak cutoff while it loops.

Which synthesizer should a beginner start with?

Start with a simple subtractive synth that ships with your DAW, then add one free wavetable synth once filters and envelopes feel familiar. Fewer controls means you hear what each one does.

In Ableton Live, Drift is built on subtractive synthesis for quick sound design with minimal CPU, and Wavetable combines two wavetable oscillators with two analog-modeled filters^[8]. Logic Pro includes Retro Synth and ES2 for FM and analog-style sounds, plus Alchemy, which Apple mentions in its wavetable and granular notes^[6][7]. For a free option in any DAW, Vital's Basic tier is free and includes the full synth with all features, 75 presets and 25 wavetables^[9].

When you want to compare more options, the ranked list of free synthesizers is a good next stop, and the sampler explainer shows the recorded-audio side of sound design. Plugg Supply's free presets are a quick way to see how finished patches are built: open one, then switch each module off in turn to hear what it contributes.