Taming sox

Bart Massey and Claude Code

Source: https://github.com/pdx-cs-sound/taming-sox.

Licensed under CC-BY 4.0.

Introduction

Sox is a command-line audio Swiss Army knife: it converts formats, applies DSP effects, mixes files, generates tones, and slots cleanly into shell pipelines. Its CLI is genuinely strange — effects come after the output filename, format flags are positional, and a typo can silently mean something completely different. This tutorial introduces those quirks in an order that makes them feel inevitable rather than arbitrary.

What this book covers. Sox has many more effects than any one tutorial can reasonably teach. The approach here: show the arguments that teach concepts — the q/t/h/l shapes in fade, the Q/Hz/octaves units in equalizer, the transfer-function syntax in compand. For arguments that just tune existing behavior, the sox man page is the right reference. When an effect is mentioned only in passing, that’s why.

Sox has real limits — they’re collected at the end of the last chapter if you want to check whether it fits your problem before investing in learning it.

Sample audio files are provided; test tones are generated as we go.

sox and sox_ng

Original sox stopped releasing in 2015. In 2024 a community fork, sox_ng, picked up active development. Most modern distros now ship sox_ng under the name sox — when this book says “sox,” it means whichever binary you have. Everything here works on both. A handful of features in the later chapters are sox_ng 14.5+ only; those are called out where they come up.

The title of this book stays Taming sox because the command is still sox. “sox_ng” only comes up when the fork itself is the subject.

Getting sox

Most modern distros ship sox_ng under the name sox. Some older stable releases still ship the 2015 legacy build. Homebrew and the BSDs vary.

Run sox --version to check. SoX_ng means you’re set. SoX 14.4.2 means you have the legacy build — everything in this book still works, but you’ll miss the sox_ng-flagged features later, and you’ll be running an unmaintained binary.

If your platform doesn’t ship sox_ng and you want it, build from https://codeberg.org/sox_ng/sox_ng. Windows binaries are on the releases page.