I've made sound effects the slow way before. For Oso Sigiloso I walked around with a recorder, performed the sounds, cleaned the takes, and exported every file by hand. I still love that process.
But games also need rain, wind, impacts, and whooshes in families of related variations. Nielo SFX turns those repeatable sounds into recipes.
Nielo SFXOpen the free web app
Sound as a Graph
A sound starts with small pieces: oscillators, noise, filters, envelopes, gain, and panning. Nodes combine them into something recognizable. A droplet becomes a reusable composite; repeated droplets become rain; noise and wind give it distance and weight.
The main Rain sound is built entirely this way. There is no hidden recording. You can open a composite, trace the signal, listen to any stage, and see its waveform directly on the node.
A Readable Recipe
Every sound lives in a readable .nielo.json document. The source editor and node graph are two views of the same file: change either one and the other follows. If the text becomes invalid, the last working sound stays available while the editor explains what needs fixing.
That same document works in the browser and from the command line. The analyzer shows the waveform, spectrogram, peak level, and RMS after each render. The synthesis engine runs in TypeScript workers; WebAudio only plays the finished buffer. Automated checks can spot an unexpected change, but I still make the final call with my ears.
Variation Without Starting Over
Procedural audio needs randomness, but it should still be repeatable. Every distribution begins with an explicit seed. Variation changes the seed to create a related take; keeping it recreates the same sound.
The exporter can produce one WAV, separate stems, or a ZIP across several seeds. One rain recipe becomes a useful set of game assets without losing the path back to any of them.
Nielo SFX is part of Nielo, a family of free creative tools built around the same idea: keep the work visible, understandable, and reproducible.
