Acid sound design

How to Make an Acid 303 for Psytrance

By Psiger · Updated July 2026

Watch the full breakdown

Acid does not need a real 303 or a complicated patch. It is a single saw wave through a resonant low-pass filter, with the filter moving on every note. Psiger used this exact approach on his own track The Acid Apple, and it comes down to a handful of settings.

The video demos the sound, then breaks the full patch down and shows how to rebuild it on any synth, because the technique matters more than the plugin. Here is the breakdown.

Key takeaways
  • Acid is one saw wave through a resonant low-pass filter. No layering needed.
  • Crank the filter resonance so it sings, then drive the cutoff with an envelope on every note.
  • The per-note filter sweep is the whole acid character. That is what makes it squelch.
  • Accent certain notes so the filter opens further, giving the line its bouncing rhythm.
  • The technique ports to any synth with a saw, a resonant filter and an envelope to cutoff.

The acid sound demo

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The acid sound demo — screenshot from the video

The target is that squelchy, resonant acid bark: a simple saw wave that comes alive when the filter opens and closes. Hearing it first tells you what you are aiming for before you start tweaking.

Notice it is one oscillator. All the character is coming from the filter movement and resonance, not from stacked layers.

The full acid patch breakdown

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The full acid patch breakdown — screenshot from the video

The patch is a saw into a resonant low-pass filter. Crank the resonance so the filter sings, then drive the cutoff with an envelope so it snaps open on each note and closes again. That per-note filter sweep is the entire acid character.

The powerful part is the accent: emphasise certain notes so the filter opens further on them, giving the line its bouncing, talking rhythm instead of a flat repeat.

Make it work on any synth

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None of this is Serum-specific. Any synth with a saw, a resonant low-pass filter, and an envelope you can route to the cutoff will do it. The recipe is the same: high resonance, envelope on cutoff, accented notes.

Learn the technique, not the preset, and you can pull an acid line out of whatever synth is in front of you.

Common questions

Psytrance production FAQ

Do I need a real 303 or a special plugin for acid?

No. An acid sound is just a saw wave through a resonant low-pass filter with an envelope moving the cutoff on each note. Any synth that has those three things, including Serum, Sylenth or a stock DAW synth, can make a convincing acid line. The technique matters far more than the plugin.

What makes an acid line sound powerful instead of flat?

Accents. If the filter opens the same amount on every note, the line sounds static. Emphasise certain notes so the cutoff snaps further open on them, and the line starts to bounce and talk. That per-note variation in filter movement is the secret to a lively acid pattern.

Where does the acid character actually come from?

From the resonant filter, not the oscillator. High resonance makes the filter ring, and driving the cutoff with an envelope on each note creates the squelching sweep. The saw is just the raw fuel. Spend your time on the filter and its envelope, not on the oscillator.