Move the Featured Image box into the main column
<?php
function customposttype_image_box() {
remove_meta_box( 'postimagediv', 'music', 'side' );
add_meta_box('postimagediv', __('Custom Image'), 'post_thumbnail_meta_box', 'music', 'normal', 'high');
}
add_action('do_meta_boxes', 'customposttype_image_box');
?>