On the PlayStation Vita, RAM is a precious resource (512MB unified). A standard uncompressed CD-quality audio track consumes about 10 MB per minute. By using at9tool.exe to compress audio to 128kbps, that same minute of audio consumes roughly 1 MB. This 10:1 compression ratio is vital for fitting large open-world games onto cartridges.
The tool operates directly through the Windows Command Prompt or terminal. The two most foundational operations are: at9tool.exe