Convert m4a to mp3
Convert m4a to aac
Note: Converting files to mp3s or aac (using the proper compression) works by leaving out bits of the original sound. It is assumed that these changes cannot be noted because they are masked by other sounds. However, converting mp3 or aac files to an uncompressed format (such as WAV) cannot restore those missing sounds. So, if you ever convert mp3s to wav audio files, keep in mind that you are maintaining the same quality and just making the files a lot bigger.
