Here are two of the best howlers I have made. They are easy to play loud or quiet. The ivory tone board is very hard and makes a most beautiful howl. The ivory warthog tusk tone boards are tenoned into the horns and glued with epoxy. The tone boards are made free-hand on a band saw then tuned to sound like a pack of coyotes.
(http://i37.photobucket.com/albums/e90/ninthinning/DSC02551.jpg)