Getting Started | a9a Docs

What a9a does

a9a is a tool for adjusting the volume, fades, and loops of audio material — sound effects, voice, BGM — before exporting it.

Loaded files are listed side by side, so you can compare waveform, loudness (LUFS), true peak, LRA, crest factor, sample rate, bit depth, channel count, and length across the whole set. When you spot the outliers, you can apply adjustments to just the selected files or to every loaded file at once.

All editing in a9a is non-destructive. Applying gain, loudness, fades, loops, or trims leaves the original file untouched. Your adjustments are written to a file when you bounce (export).

Supported formats

Format	Read	Write
WAV	Yes	Yes
FLAC	Yes	Yes
AIFF / AIFF-C (`.aif` / `.aiff` / `.aifc`)	Yes	Yes
Ogg Vorbis (`.ogg` / `.oga`)	Yes	Yes
MP3	Yes	Yes (requires LAME)
AAC (`.m4a` / `.aac`, AAC-LC / HE-AAC v1 / HE-AAC v2)	Yes	Yes

AAC usually works out of the box

In the following cases, the libfdk-aac shared library is required:

Exporting on Windows with anything other than AAC-LC CBR at 96/128/160/192 kbps and 44.1/48 kHz (this includes HE-AAC and VBR)
Exporting AAC-LC at 88.2/96 kHz on macOS
Reading or writing AAC on Linux
Explicitly selecting fdk-aac as the Encoder

Otherwise no additional installation is required: AAC uses AudioToolbox on macOS and Media Foundation on Windows.

Install it as follows.

Windows: obtain a libfdk-aac DLL (libfdk-aac-2.dll, libfdk-aac.dll, or fdk-aac.dll) and place it in the same folder as the executable or in a folder on PATH
macOS: run brew install fdk-aac with Homebrew
Linux: install libfdk-aac.so.2 from your distribution’s packages (for example, sudo apt install libfdk-aac2 on Debian / Ubuntu; Fedora’s stock fdk-aac-free covers AAC-LC only, so use RPM Fusion’s fdk-aac for HE-AAC)

Your first five minutes (GUI)

The shortest path from loading files to exporting them at a consistent loudness.

Load files. Choose Open... in the Files menu, or drag and drop from Finder / Explorer onto the list area. You can load multiple files at once.
Compare them. Click the Loudness or True Peak column header to sort, and the files that stand out — too loud or too quiet — surface immediately.
Fix them in one pass. Open Loudness > All... from the Edit menu, enter your target in Target Integrated Loudness (LUFS), and press Apply. The Loudness column updates.
Export. Open Bounce > All... from the Files menu, set Output Directory, and run it.

The whole a9a window. The list of loaded files sits in the center, the detail view below it, the playback transport along the bottom, and the level meters on the right. — The window after loading files: 1: list, 2: detail view, 3: transport, 4: level meters

The same thing in the CLI

Start by inspecting the current state with probe.

a9a_cli probe *.wav

Then apply the same loudness adjustment to every file with render. Adding --same-format keeps each output in the format of its input.

a9a_cli render *.wav \
  --out-dir out \
  --same-format \
  --op loudness target=-16LUFS max-true-peak=-1dBTP

This page was written with generative AI.