Synthesis and sound design · updated 2026-08-16

ALIASING

Digital artefacts created when harmonics go above half the sample rate and fold back down as inharmonic junk.

Synthesis and sound design — Close-up of a Eurorack modular synthesizer: oscillator, filter and envelope modules wired together with patch cables, showing the signal path these synthesis terms describe.

Key takeaways

Digital artefacts created when harmonics go above half the sample rate and fold back down as inharmonic junk.
Bright waveforms, hard sync and distortion are the usual sources.
Play a bright digital saw two octaves up: if the top harmonics descend rather than ascend, you are hearing aliasing.
Watch out: fixing aliasing with a low-pass filter after the fact.
Sits under synthesis and sound design in this glossary, with 2 primary sources below.

Quick checklist

Can you define aliasing in one sentence without looking?
Can you point at aliasing in a real session, mix or contract?
Have you tried the practical move above at least once?
Would you catch the common mistake before it costs you a take?
Have you opened one of the primary sources below rather than a forum thread?

ALIASING IN DEPTH

Aliasing happens when a system generates frequencies above half the sample rate; they fold back down and appear as inharmonic tones that move the wrong way as you play up the keyboard. Bright waveforms, hard sync and distortion are the usual sources.

How it works in practice

Play a bright digital saw two octaves up: if the top harmonics descend rather than ascend, you are hearing aliasing.

The mistake people make

Fixing aliasing with a low-pass filter after the fact. The folded content is already inside the audible band; enable oversampling in the source instead.

WHERE ALIASING SITS

Aliasing belongs to synthesis and sound design in the Sampled music glossary. How synths make sound, in the order the signal actually travels.

TERMS THAT DEPEND ON ALIASING

Nyquist frequency
Half the sample rate — the highest frequency a digital system can represent. Above it, content folds back as aliasing, so converters filter it out.

TEST YOURSELF

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3 quick questions on aliasing. Answers are marked instantly — nothing is sent anywhere.

1. Which statement best describes aliasing?
2. What is the mistake people most often make with aliasing?
3. In practice, which of these applies to aliasing?

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SOURCES AND CITATIONS

Free, primary references for aliasing — standards bodies, manufacturers, government offices and university course material. Each one lists the line of this entry it backs up.

Xiph.org — digital audio primer (opens in a new tab)
Open-source standards group · Xiph.Org Foundation
“Digital artefacts created when harmonics go above half the sample rate and fold back down as inharmonic junk.”— the claim this source supports
Why it counts: Xiph's write-ups are free, technically rigorous and famously careful about the myths around digital audio.
Stanford CCRMA — DSP texts (opens in a new tab)
University research centre · Stanford CCRMA
“Aliasing happens when a system generates frequencies above half the sample rate; they fold back down and appear as inharmonic tones that move the wrong way as you play up the keyboard.”— the claim this source supports
Why it counts: The CCRMA course material derives this from first principles, so you can check the maths behind the plain-English version above.

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