functions.php

<?php

/**
 * Limit Blog to Musing Category
 *
 * @author Bill Erickson
 * @link http://www.billerickson.net/customize-the-wordpress-query/
 */
function be_blog_query( $query ) {
  if( $query->is_main_query() && $query->is_home() && !is_admin() )
    $query->set( 'category_name', 'musings' );
}
add_action( 'pre_get_posts', 'be_blog_query' );