$querystr = "
    SELECT wposts.* 
    FROM $wpdb->posts wposts, $wpdb->postmeta wpostmeta, $wpdb->terms wterms
    WHERE wposts.ID = wpostmeta.post_id 
   	AND wterms.name = 'Song'
    AND wpostmeta.meta_key = 'artist_tag' 
    AND wpostmeta.meta_value = '$artist' 
    AND wposts.post_status = 'publish' 
    AND wposts.post_type = 'post' 
    AND wposts.post_date < NOW() 
    ORDER BY wposts.post_date DESC
 ";