functions.php

<?php
function alphaindex_queries( $query ) {
	/* Sort songs alpha  */
	if ( ! is_admin() && ( is_post_type_archive( 'song' ) || is_tax( 'alpha' ) ) && $query->is_main_query() ) {
		$query->set('orderby', 'name');
		$query->set('order', 'ASC');
	}
}
add_action( 'pre_get_posts', 'alphaindex_queries' );