Audacity is a free and open-source digital audio editor and recording application software. The supported audio formats for importing, processing, and exporting include WAV, WMA, MP3, AAC, AIFF, FLAC, AC3, AMR, and OGG Vorbis files. It supports up to two channels of simultaneously recording from microphones, USB, or Firewire devices. The audio tracks can be cut, copy, paste, mixed, or you can change the recording speed and amplitude. With some effects, you can change your voice, remove background noise, remove the voice from a stereo song, etc. All these features can be found in the Audacity Manual.
You can find the latest version of Audacity at https://www.audacityteam.org/ on the Download menu.