Audacity is a free, easy-to-use audio editor and recorder for Windows, Mac OS X, GNU/Linux, and other operating systems. You can use Audacity to:

• Record live audio.
• Convert tapes and records into digital recordings or CDs.
• Edit Ogg Vorbis, MP3, and WAV sound files.
• Cut, copy, splice, and mix sounds together.
• Change the speed or pitch of a recording.
• Import and export WAV, AIFF, AU, and Ogg Vorbis files.
• Import MPEG audio (including MP2 and MP3 files) with libmad.
• Export MP3s with the optional LAME MP3 encoder library.
• Create WAV or AIFF files suitable for burning to CD.
• Import and export all file formats supported by libsndfile.
• Open raw (headerless) audio files using the “Import Raw” command.

It supports all common editing operations, 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.

What's New in version 1.3.9 Beta:

Bug fixes for:

• Crash, slow launch or excessive CPU/memory use arising from automatic VST support:
  • VST instrument plug-ins should now be correctly ignored
  • VST effects now scanned only at start of first session that detects them, then cached
  • Effects are now not loaded or opened until needed
  • New "Effects" tab in Preferences to enable/disable VST effects and enable VST rescan on next launch
• Default View Mode now works
• Chains now always apply their stored parameters rather than those last used in Effect menu
• Non-MP3 files imported via drag or Recent Files caused crash if filter in file open window set to MP3
• AAC exports (using the optional FFmpeg library) silenced
• Generating audio always fitted the project in the window; fit now done only if generating in new track
• View menu items/shortcuts incorrectly disabled when playing or recording
• DTMF generator defaulted to zero duration on open
• Unwanted interactions between linked audio and label tracks
• (Windows XP) Failure to launch on some machines due to "incorrect configuration" issue
• (Windows) Crash importing a stereo file while a screen reader such as JAWS is running
• (Mac OS X) :
  • Audio Units effects applied to all tracks in project even if not selected
  • QuickTime importer now handles files greater than 16-bit or 64000 Hz
• Various other interface bugs

Improvements:

• Compressor: new option to compress based on peaks, improved attack and decay time support
• Mixer Board: improved design, more responsive meters and now interacts fully with Track Panel in main window