Logic Pro 7.2.1 converts some compressed files to AIFF

Logic Pro 7.2.1 is now able to play compressed audio files directly. In some cases, when an MP3 or AAC file is added to a song, the file is rendered as AIFF instead.

Solution

An MP3 or AAC file must meet these technical requirements for Logic Pro to play it directly:

• 44.1 kHz
• Bit rate of at least 32kbps (mono) or 48kb/sec (stereo)
• Created by iTunes 5 or later, or by Logic 7.0 or later

You can still use compressed files that do not meet all of these conditions, but they have to be rendered as AIFF first.