Audacity is a program that lets you manipulate digital audio
waveforms. In addition to letting you record sounds directly from
within the program, it imports many sound file formats, including
WAV, AIFF, AU, IRCAM, MP3, and Ogg Vorbis. It supports all
common editing operations such as Cut, Copy, and Paste, plus it will
mix tracks and let you apply plug-in effects to any part of a sound. It
also has a built-in amplitude envelope editor, a customizable
spectrogram mode and a frequency analysis window for audio
analysis applications.

WWW: https://www.audacityteam.org/