I have got a Macbook Pro 15' that has both an audio in and out port. Now I would like to play the sound from an external device through the speakers of my Mac. The program can mix and split audio files, edit silences, reduce or eliminate background noise, integrate filters and special effects, and even convert a mono audio file into stereo. The program’s layout is clean and intuitive, and meant to encourage a smooth workflow.

Audacity is a free audio recorder/editor/mixer. You can record sounds, play sounds, import and export WAV, AIFF, and MP3 files, and more. Use it to edit your sounds using Cut, Copy and Paste (with unlimited Undo), mix tracks together, or apply effects to your recordings. It also has a built-in amplitude envelope editor, a customizable spectrogram mode, and a frequency analysis window for audio analysis applications.

Built-in effects include Bass Boost, Wahwah, and Noise Removal, and it also supports VST plug-in effects. Note: While the software is classified as free, it is actually What's New in Audacity. Audacity is a free audio recorder/editor/mixer. Macaroni and cheese rue. You can record sounds, play sounds, import and export WAV, AIFF, and MP3 files, and more. Use it to edit your sounds using Cut, Copy and Paste (with unlimited Undo), mix tracks together, or apply effects to your recordings. It also has a built-in amplitude envelope editor, a customizable spectrogram mode, and a frequency analysis window for audio analysis applications. Built-in effects include Bass Boost, Wahwah, and Noise Removal, and it also supports VST plug-in effects.

Note: While the software is classified as free, it is actually donationware. Please consider making a donation to help support development.