音栓

Appears to be a Japanese coinage from Middle Chinese-derived roots, as a compound of 音 (on, “sound”) +‎ 栓 (sen, “stop, stopper, plug, cork”).

• (Tokyo) おんせん [òńséń] (Heiban – [0])^[1]
• IPA^(key): [õ̞ɰ̃sẽ̞ɴ]

音(おん)栓(せん) • (onsen) 

1. (music) a stop or register in an organ or similar musical instrument

   Synonym: ストップ (sutoppu)

• Shōgaku Tosho (1988) 国語大辞典（新装版） [Unabridged Dictionary of Japanese (Revised Edition)] (in Japanese), Tōkyō: Shogakukan, →ISBN
• Matsumura, Akira, editor (1995), 大辞泉 [Daijisen] (in Japanese), First edition, Tokyo: Shogakukan, →ISBN
• “音栓”, in ブリタニカ国際大百科事典 小項目事典 (Buritanika Kokusai Dai Hyakka Jiten: Shō Kōmoku Jiten, “Encyclopædia Britannica International: Micropædia”)‎^[1] (in Japanese), Tōkyō: Britannica Japan Co., Ltd., 2014
• “音栓”, in 改訂新版 世界大百科事典 (Kaitei Shinpan Sekai Dai-hyakka Jiten, “Heibonsha World Encyclopedia Revised Edition”)‎^[2] (in Japanese), Tōkyō: Heibonsha, 2007, →ISBN