Problem adding MP3 attachments to a jPlayer playlist

Have a look at wp_localize_script for passing php data to javascript. A pseudo-code example:

$tracks = array();

foreach( $mp3_attachments as $mp3_attachment ):
    $tracks[] = array(
        'mp3' => $mp3_attachment['filename'],
        'title' => $mp3_attachment['title']
    );
endforeach;

$wpa_track_data = array( 'tracks' => $tracks );

wp_enqueue_script( 'wpa_script', get_template_directory_uri() . '/js/yourscript.js' );
wp_localize_script( 'wpa_script', 'wpa_data', $wpa_track_data );

Then in your js wpa_data.tracks will contain your array of mp3s and titles.