Audacity

Around since 2000 and still the standard answer to recording a podcast or cleaning up a voice track without paying for anything. It records multiple tracks, edits on a waveform, and covers what most creators need: trimming, levelling, noise reduction, EQ, compression and export.

It shows its age in places. The interface is unfashionable, the workflow is built around applying changes to the waveform, so reversing a decision later takes more work than in a session-based editor, and it handles audio alone, which makes anything synced to picture easier in your video editor. For an interview recording, a voiceover clean-up or a single problem file, it does the job and costs nothing.