‘Hoon’ is a traditional musical instrument known to be coming into our country in King Yejong of Koryo Dynasty. Because of the structural problem, the traditional Hoon has a limited musical range. Nowadays Hoon is played only in Confucian ritual music among Korean traditional music. Our research team have developed the improved Hoon which retains the sound of the traditional Hoon, as we can play western music as well as traditional music by this instrument. This new instrument has been tested with the traditional Hoon and Ocarina, and very promising experimental results have been obtained. The pitch of the sound of Hoon is well suited to harmonic scale, and the range of sound has been expanded while retaining timbre compared to that of the traditional Hoon.