audio editing
Audacity:
Audacity is a free and open program for digital audio editing and recording. It is available for Windows, macOS and Linux. Audacity is able to record from multiple sources, add effects and manipulate the audio signal. It is possible to save the recording in all common audio formats.
VLC:
The VLC media player is an open source program for playing back video and audio files. The program is available for all current platforms, including mobile ones, and enables playback of all current audio formats. Furthermore, it is possible to transcode audio formats, i.e. to convert them into another format/codec.