Query posts by subfield

Hi! Loving metabox! I need to use get_posts() (or some alternative) to query posts by subfield. Let's take as an example the very same code from the documentation:

add_filter( 'rwmb_meta_boxes', 'meta_box_group_demo_register' );
function meta_box_group_demo_register( $meta_boxes ) {
	$meta_boxes[] = array(
		'title'  => __( 'Album Tracks' ),
		'fields' => array(
			array(
				'id'     => 'standard',
				// Group field
				'type'   => 'group',
				// Clone whole group?
				'clone'  => true,
				// Drag and drop clones to reorder them?
				'sort_clone' => true,
				// Sub-fields
				'fields' => array(
					array(
						'name' => __( 'Track name', 'rwmb' ),
						'id'   => 'text',
						'type' => 'text',
					),
					array(
						'name' => __( 'Release Date', 'rwmb' ),
						'id'   => 'date',
						'type' => 'date',
					),
					array(
						'name'    => __( 'Genre', 'rwmb' ),
						'id'      => 'genre',
						'type'    => 'select_advanced',
						'options' => array(
							'pop'  => __( 'Pop', 'rwmb' ),
							'rock' => __( 'Rock', 'rwmb' ),
						),
					),
				),
			),
		),
	);
	return $meta_boxes;
}

How can I query posts by 'genre' or any other field?