横笛(おうてき)ōteki
Ōteki
Literally “transverse flute” and originally a generic term for all such, it now is used interchangeably with the ryūteki, which is played in gagaku music of the left (sahō). Though most are bamboo, the Shōsō-in contains a stone ōteki as well.
67th Annual Exhibition of Shōsō-in Treasures, 2015