您可以将此部分添加到函数中：

$audios =& get_children(\'post_type=attachment&post_parent=\'.$post->ID.\'&post_mime_type=audio\' );
foreach ( $audios as $id => $audio ){ 
    $content.=\'<a href="\'.wp_get_attachment_url($id).\'" target="_blank">\'.$audio->post_title.\'</a> \';
} 

我正在使用get_children() 在这里，您可以在这里阅读更多信息：

http://codex.wordpress.org/Function_Reference/get_children

Edit:

function featuredtoRSS($content) {
    global $post;

    if ( has_post_thumbnail( $post->ID ) ){
        $content = \'\' . get_the_post_thumbnail( $post->ID, \'topImage\', array( \'style\' =>  \'margin:0 auto; border: 1px solid #555; display:block;\' ) ) . \'\' . $content;
    }

    $audios =& get_children( \'post_type=attachment&post_parent=\'.$post->ID.\'&post_mime_type=audio\' );
    foreach ( $audios as $id => $audio ){ 
        $content.=\'<a href="\'.wp_get_attachment_url($id).\'" target="_blank">\'.$audio->post_title.\'</a> \';
    } 

    return $content;
}

add_filter(\'the_excerpt_rss\', \'featuredtoRSS\');
add_filter(\'the_content_feed\', \'featuredtoRSS\');