Audacity is a free, open-source software for recording and editing sounds. Available for Windows, Mac, and GNU/Linux. Download Audacity here. Make sure to download the additional Lame MP3 encoder if you want to export your audio as an mp3 file.
Record live audio.
Supports basic audio editing; splicing, mixing, changing pitch or speed.
Works only with Ogg Vorbis, MP3, WAV or AIFF sound files.