Error: Class 'Chord' not found

<?php
define('BASE_PATH', dirname(__DIR__));
define('APP_PATH', BASE_PATH . '/app');
 
date_default_timezone_set('Asia/Jakarta');
 
error_reporting(E_ALL);
ini_set('display_errors', 1);
 
require(BASE_PATH . '/vendor/autoload.php');
 
use Phalcon\Di\FactoryDefault;
use Phalcon\Debug;
 
// Enable Phalcon debug screen
$debug = new Debug();
$debug->listen();
 
try {
    $di = new FactoryDefault();
 
    include APP_PATH . '/config/router.php';
    include APP_PATH . '/config/services.php';
 
    $config = $di->getConfig();
    include APP_PATH . '/config/loader.php';
 
    $application = new \Phalcon\Mvc\Application($di);
    echo $application->handle($_SERVER['REQUEST_URI'])->getContent();
 
} catch (\Exception $e) {
    // Temporarily disable redirect for debugging
    // header('location:' . $config->application->baseUri . '404');
    // die($e->getMessage());
 
    echo '<pre>' . $e . '</pre>';
}