CDA or CD Audio files are not the audio files but the depictions of CD audio tracks, because they do not contain sampled sound at all. They are just a method that Mac uses to let you access an Audio CD index. This is why if you would copy a .CDA file to the hard drive and try to play it with an audio player, nothing would happen. And you would need the CDA to MP3 Converter to extract audio tracks from the CD. To play music tracks on your CD you need first to convert them to WAV, MP3 or another file format that system can identify Some media players, such as Mac Media Player and Apple iTunes, can grab the audio files from the CDs to your media library in the selected audio format.