I can't believe I forgot about Jeff Agrell's kudu horns. Pictured is a Kudu, a type of Gazelle, and the instruments made from their horns. The set Jeff has is pitched in E pentatonic (each horn plays one note). The highest pitched horn has a finger hole so that it will play two notes. These horns are played all over Africa and are usually used in a rhythmic hocket texture often accompanying a marimba. You can read more about them as well as some other African instruments here.