There is a fun new PHP extension that has been developed (called ffmpeg-php) that allows you to access audio and video content directly through a PHP interface.

ffmpeg-php ffmpeg-php is an extension for PHP that adds an easy to use, object-oriented API for accessing and retrieving information from video and audio files. It has methods for returning frames from movie files as images that can be manipulated using PHP's image functions. This works well for automatically creating thumbnail images from movies. ffmpeg-php is also useful for reporting the duration and bitrate of audio files (mp3, wma...). ffmpeg-php can access many of the video formats supported by ffmpeg (mov, avi, mpg, wmv...)

I've seen other projects that work with audio files (like mp3s) to provide the information for them, but I hadn't seen anything similar to this as of yet. It does require that you install the ffmpeg software, so if you're on shared hosting, you might not be in luck...