index.php

<?php
function alphaindex_alpha_tax() {
	register_taxonomy( 'alpha',array (
		0 => 'song',
	),
	array( 'hierarchical' => false,
		'label' => 'Alpha',
		'show_ui' => false,
		'query_var' => true,
		'show_admin_column' => false,
	) );
}
add_action('init', 'alphaindex_alpha_tax');