Question: S. R. D. Vaidyanathan was an Indian musician who played which double reed wind instrument?
Context: The ottu (or otter) is a double reed wind instrument, used in Carnatic music of Southern India to provide a drone accompaniment to the similar nadaswaram oboe.  Like the nadaswaram, the ottu is a large conical instrument, some two and a half feet long.  Unlike the nadaswaram, the ottu has no fingerholes, being intended to produce one constant note while playing.  It is provided with several small tuning holes which can be stopped with wax to modify its note. Kuzhal pattu is a form of traditional temple music practised in the Kerala state of India.  It centers on the use of the kuzhal, a double reed wind instrument, and is typically performed at temple festivals. The guan () is a Chinese double reed wind instrument.  The northern Chinese version is called guanzi (管子) or bili (traditional: 篳篥; simplified: 筚篥) and the Cantonese version is called houguan (喉管).  It is classified as a bamboo instrument in the Ba Yin (ancient Chinese instrument classification) system.  Unlike other instruments in the double-reed family of woodwinds which mostly have conical bores, such as the Chinese "suona" or the Western oboe, the "guan" has a cylindrical bore, giving its distinctive mellow, yet piercing buzz-like timbre. The algaita (also spelled "alghaita", "algayta" or "algheita") is a double reed wind instrument from West Africa, especially among the Hausa and Kanuri peoples. Its construction is similar to the oboe-like rhaita and the zurna.  The algaita is distinguished from these other instruments by its larger, trumpet-like bell.  Instead of keys, it has open holes for fingering, similar to the zurna. S. R. D. Vaidyanathan (Tamil: S.R.D. வைத்தியநாதன்; 15 March 1929 − 18 November 2013) was an Indian musician who played the Nadhaswara. The kèn bầu (] ) is one of several types of kèn, a double reed wind instrument used in the traditional music of Vietnam.  It is similar in construction and sound to the Chinese "suona" and the Korean "taepyeongso".  It comes in various sizes and is a primary instrument of the music of the former royal court music of Huế. The kuzhal is a traditional double reed wind instrument used in the south Indian state of Kerala.  It is similar in construction to a "nagaswaram" or a large "shehnai", and has a very shrill and penetrating tone. A szopelka is a Russian double reed wind instrument, similar in form to the zurna.  Typically, the instrument is 15 in long, with a brass mouthpiece and a wooden body with fifteen finger holes, eight large and seven small. The nadaswaram, nagaswaram, nadhaswaram or nathaswaram is a double reed wind instrument.  It is a traditional classical instrument used in Tamilnadu, Andhra Pradesh, Karnataka, and Kerala. The taepyeongso (lit.  "big peace wind instrument"; also called hojok, hojeok 호적 胡笛, nallari, or saenap, 嗩吶) is a Korean double reed wind instrument in the shawm or oboe family, probably descended from the Persian zurna and closely related to the Chinese suona.  It has a conical wooden body made from "yuja" (citron), "daechu" (jujube), or yellow mulberry wood, with a metal mouthpiece and cup-shaped metal bell.  It originated during the Goryeo period (918 – 1392).
Answer: The nadaswaram,