WordPress | Loop | Order | pre_get_posts

loop_order_change.php

<?php
// This alters the main loop (loop.php) to order Archive queries by Title
function archive_posts($query) {
    if ( $query->is_archive() ) {
	$query->set( 'orderby', 'title' );
        $query->set( 'order', 'asc' );
    }
}
add_action('pre_get_posts', 'archive_posts');
?>

Loop change

The main loop.php template just dishes out the posts in date order by default. Here we use pre_get_posts to change the order of the query when it is an archive.

This needs adding to functions.php.