$query_args = array(
    'post_type' => 'listing',
    's' => get_query_var( 's' ),
    'posts_per_page' => 10,
    'paged' => $paged
);

$query_args = array(
    'post_type' => 'listing',
    'tax_query' => array(
        'relation' => 'OR',
          array(
              'taxonomy'  => 'genre',
              'field'     => 'slug',
              'terms'     => array(...)
          ),
          array(
              'taxonomy'  => 'decade',
              'field'     => 'slug',
              'terms'     => array(...)
          )
    ),
    'posts_per_page' => 10,
    'paged' => $paged
);