Eu quase nunca fiz qualquer configuração do Apache, mas levei 2 minutos para encontrar isso:
By default successive RewriteCond directives are linked by a logical AND. There is an optional modifier, [OR], that allows you to chain the next RewriteCond with a logical OR.
Isso deve funcionar:
RewriteEngine on
RewriteCond %{HTTP_HOST} ^.*\.auricle\.fm [NC]
RewriteCond %{HTTP_HOST} !=chat.auricle.fm [NC]
RewriteRule ^(.*)$ http://auricle.fm/$1 [L,R=301]