Retro SFX Generator

How to make a sound effect

Five steps. The order matters more than it looks — generating first and refining second is faster than building a patch from silence.

1. 1

   Start from a generator, not from silence

   Pick one of the seven generators — Pickup, Laser, Explosion, PowerUp, Hit, Jump or Blip. Each one randomises the whole patch inside the range that produces that class of sound, so you get something usable on the first click rather than hunting through twenty sliders. This is how sfxr-style tools are meant to be used: generate first, refine second.

2. 2

   Narrow it with a genre preset

   The eight genre presets bias the same generators toward a house style: Platformer for bright coins and jumps, RPG for soft interface blips, Metroidvania for ability unlocks and doors, Shooter for lasers and impacts, Puzzle for clean confirmations, Sci-Fi for phased digital tones, Fantasy for sparkly pickups, Horror for low noise stingers. They are starting points, not locks — every slider stays editable.

3. 3

   Shape the envelope before you touch anything else

   Attack, Sustain, Punch and Decay decide whether a sound reads as a tap, a hit or a drone, and they matter more than the waveform. A short attack with a hard punch and a fast decay gives you an impact; a slow attack with a long sustain gives you a hum. If a sound feels wrong, it is usually the envelope, not the pitch.

4. 4

   Mutate and compare instead of guessing

   Mutate nudges the current patch slightly, which is how you find the version of a sound that is almost right. Generate 4 variations renders four alternatives side by side without overwriting what you have, so you can audition against your current patch rather than losing it. Use the waveform view and spectrum analyser to see clipping or a decay that runs longer than you think.

5. 5

   Export WAV, then take the engine snippet

   Download WAV gives you a 44.1 kHz 16-bit mono file that is sample-accurate — nothing is re-encoded. The Godot, Unity and Web Audio tabs give you the few lines needed to play that file in each engine, and Clipboard JSON copies the full parameter patch so you can save a sound in source control and rebuild it exactly later.

What every control does

The control set follows the sfxr model, so this reference carries over to any tool in that family.

WaveformSquare · Sawtooth · Sine · Noise

The oscillator the whole patch is built on. Square is the classic chiptune voice and the right default for coins, jumps and blips. Sawtooth is harsher and cuts through a busy mix, which suits lasers and engines. Sine is pure and soft, good for gentle interface tones. Noise has no pitch at all — it is the basis of explosions, footsteps and hits, and pitch controls affect it only through the filters.

EnvelopeAttack · Sustain · Punch · Decay

Attack is how long the sound takes to reach full volume, Sustain how long it holds, Decay how long it takes to fall away. Punch adds a short volume spike at the start of the sustain — it is what makes an impact feel like it has weight rather than just being loud. Together these four decide the character of the sound more than any other group.

FrequencyPitch · Slide · Delta slide · Minimum frequency

Pitch sets the starting frequency. Slide moves it over the life of the sound: sliding up reads as a pickup or power-up, sliding down as a laser or a fall. Delta slide accelerates that movement, which is what gives a laser its snap rather than a even glide. Minimum frequency stops the pitch falling below a floor, so a downward slide ends rather than disappearing.

Vibrato and arpeggioVibrato depth · Vibrato speed · Change amount · Change speed

Vibrato wobbles the pitch continuously and in small amounts adds life to an otherwise static tone. Change amount and change speed do something different: they jump the pitch by a fixed step partway through the sound. That stepped jump is the arpeggio effect behind most classic power-up and level-complete sounds.

Square dutyDuty cycle · Duty sweep

Only affects the square wave. Duty cycle is the ratio of the high part of the wave to the low part; changing it makes a square sound thinner or fuller without changing its pitch. Duty sweep moves that ratio during the sound, which is a cheap way to get movement out of a single oscillator — a very common trick on the NES.

Filters and phaserLow-pass cutoff · Resonance · High-pass cutoff · Phaser offset and sweep

The low-pass filter removes high frequencies, which makes a sound duller and more distant; resonance emphasises the frequencies right at the cutoff and can add a vocal quality. The high-pass filter removes low frequencies and is how you stop a small interface blip from muddying a mix. The phaser sweeps a notch through the spectrum for the swirling, digital sound typical of sci-fi effects.

Getting the sound into your engine

Each export tab gives you the few lines needed to play the file, not a framework to install.

Godot 4

Drop the WAV into res://sfx/ and the Godot tab gives you an AudioStreamPlayer node that loads it and plays on demand. Godot imports WAV directly; for a project where file size matters, convert to OGG Vorbis in your import settings, which Godot handles well for short effects and music alike.

Unity

The Unity tab gives you a small MonoBehaviour that adds an AudioSource, keeps playOnAwake off, and exposes PlaySfx() using PlayOneShot so overlapping triggers do not cut each other off. Assign the exported clip in the inspector. Unity imports WAV natively and will compress on build according to your import settings.

Web and everything else

The Web Audio tab is a short fetch-and-decode helper for playing the WAV in a browser game. Clipboard JSON copies the whole parameter patch, which is the format worth committing to your repository: a WAV is an artefact, but the patch is the source, and it lets you regenerate or tweak the sound months later without guessing at slider positions.

Why the export is WAV and not MP3

WAV is written directly from the rendered samples at 44.1 kHz, 16-bit, mono, so what you download is exactly what you previewed with no lossy stage in between. Game engines want uncompressed or engine-compressed audio for short effects anyway — compressing a 200 ms blip to MP3 saves almost nothing and adds encoder padding at the start. Convert to OGG or MP3 in your own pipeline if you need it for web delivery.

Where this fits in the pipeline

• Godot 4 2D Pipeline

  Where audio sits relative to level layout, tiles, collision and economy work.

• Sprite Sheet Generator

  Pack the frames the sound effects are going to fire against.

• 2D Game Dev Lab

  Every tool in the pipeline in running order — layout, tiles, collision, sprites, audio, economy.