Lewis Short
mŏnaulos | mŏnaulus (noun M) = μόναυλος: or
* A single flute, a flute with a single pipe (post-Aug.): fistulam et monaulum (invenit) Pan Mercurii,Plin. 7, 56, 57, § 204: saepe monaulon habet,Mart. 14, 64, 2; cf. monaules.
Charlton T. Lewis, Charles Short, A Latin Dictionary