how to upload mp3 from url to wp media

As @fuxia suggest, You have to extend $wp_filetype check for mp3 also. for mp3 extenstion you can use audio/mpeg3, audio/x-mpeg-3, video/mpeg, video/x-mpeg mime types. just add check condition in try block where you check for image valid type. I have tested and it is working fine for me. let me know if this helps to you.

if ( !substr_count($wp_filetype['type'], "image") &&  !substr_count($wp_filetype['type'], "audio")) {
    throw new Exception( basename($imageurl) . ' is not a valid ' . $wp_filetype['type']  . '' );
}