Question: What reed instrument was played by Indian musician S. R. D. Vaidyanathan?

Context paragraphs:
Multireedist: A multireedist is a musician capable of performing on more than one reed instrument.  Many reed instruments are similar enough that if a musician plays one, they are expected to be able to play the other.  Examples of this are the oboe and English horn or the clarinet and saxophone.  Multireedists are valued more highly than their single instrument counterparts.  In many Broadway musicals, reed or wind parts require the performing musician to play multiple instruments during the course of the work.

Heckelphone-clarinet: The heckelphone-clarinet (or "Heckelphon-Klarinette") is a rare woodwind instrument, invented in 1907 by Wilhelm Heckel in Wiesbaden-Biebrich, Germany.  Despite its name, it is essentially a wooden saxophone with wide conical bore, built of red-stained maple wood, overblowing the octave, and with clarinet-like fingerings.  It has a single-reed mouthpiece attached to a short metal neck, similar to an alto clarinet.  The heckelphone-clarinet is a transposing instrument in B♭ with sounding range of D (middle line of bass staff) to C (two ledger lines above the treble staff), written a whole tone higher.  The instrument is not to be confused with the heckel-clarina, also a very rare conical bore single reed woodwind by Heckel but higher in pitch and made of metal, nor with the heckelphone, a double reed instrument lower in pitch.

Single-reed instrument: A single-reed instrument is a woodwind instrument that uses only one reed to produce sound.  The very earliest single-reed instruments were documented in ancient Egypt, as well as the Middle East, Greece, and the Roman Empire.  The earliest types of single-reed instruments used idioglottal reeds, where the vibrating reed is a tongue cut and shaped on the tube of cane.  Much later, single-reed instruments started using heteroglottal reeds, where a reed is cut and separated from the tube of cane and attached to a mouthpiece of some sort.  By contrast, in a double reed instrument (such as the oboe and bassoon), there is no mouthpiece; the two parts of the reed vibrate against one another.  Reeds are traditionally made of cane and produce sound when air is blown across or through them.

Bass oboe: The bass oboe or baritone oboe is a double reed instrument in the woodwind family.  It is about twice the size of a regular (soprano) oboe and sounds an octave lower; it has a deep, full tone somewhat akin to that of its higher-pitched cousin, the English horn.  The bass oboe is notated in the treble clef, sounding one octave lower than written.  Its lowest note is B (in scientific pitch notation), one octave and a semitone below middle C, although an extension may be inserted between the lower joint and bell of the instrument in order to produce a low B♭ .  The instrument's bocal or crook first curves away from and then toward the player (unlike the bocal/crook of the English horn and oboe d'amore), looking rather like a flattened metal question mark ; another crook design resembles the shape of a bass clarinet neckpiece.  The bass oboe uses its own double reed, similar to but larger than that of the English horn.

Nadaswaram: 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.

S. R. D. Vaidyanathan: S. R. D. Vaidyanathan (Tamil: S.R.D. வைத்தியநாதன்; 15 March 1929 − 18 November 2013) was an Indian musician who played the Nadhaswara.

Cornamuse: The cornamuse is a double reed instrument dating from the Renaissance period.  It is similar to the crumhorn in having a windcap over the reed and cylindrical bore.  In "Syntagma musicum" II (1619), Michael Praetorius writes: "Die CornaMuse sind gleich aus/und nicht mit doppelten/sondern mit einer einfachen Röhre/gleich den Bassanelli" ("The cornamuse are similar to/and do not have a double, but rather a single tube (bore)/like the bassanelli".)  This statement differentiates it from double bore instruments of the period like the sordun, kortholt and curtal.  Praetorius did not include a woodcut of the cornamuse, but his depiction of the bassanello has a single bore and double reed.  Another clue to its appearance is given in his description of the schryari: ("They...are nearly the same as the cornamuse in size and appearance".)  Assertions by some modern writers about the cornamuse having a single reed stem from the misreading of "Röhre" (pipe, tube, duct, canal) as "Rohr" (reed).

Bawu: The bawu (; also ba wu) is a Chinese wind instrument.  Although shaped like a flute, it is actually a free reed instrument, with a single metal reed.  It is played in a transverse (horizontal) manner.  It has a pure, clarinet-like timbre and its playing technique incorporates the use of much ornamentation, particularly bending tones.

Reed Phase: Reed Phase, also called Three Reeds, is an early work by the American minimalist composer Steve Reich.  It was written originally in 1966 for soprano saxophone and two soprano saxophones recorded on magnetic tape, titled at that time Saxophone Phase, and was later published in two versions: one for any reed instrument and tape (titled "Reed Phase"), the other for three reed instruments of exactly the same kind (in which case the title is "Three Reeds").  It was Reich's first attempt at applying his "phasing" technique, which he had previously used in the tape pieces "It's Gonna Rain" (1965) and "Come Out" (1966), to live performance.

Gralla (instrument): The gralla (] ), also known as grall de pastor, xaramita o xirimita, is a traditional Catalan double reed instrument in the shawm family.  Like the dolçaina from Valencia - a very similar instrument which many experts consider a variety of the gralla - the gralla comes from the ancient xeremia a medieval instrument largely used until the Baroque.  Probably, the name of the instrument comes from its strident sound similar to the sound of a Jackdaw native to Catalonia and northern Spain and also called 'Gralla' in Catalan.

Supporting paragraphs: S. R. D. Vaidyanathan Nadaswaram
Answer: the Nadhaswara