Basset horn a. : An instrument blown with a reed, and resembling a clarinet, but of much greater compass, embracing nearly four octaves.

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Taxonomy
basset horn, basset-horn, horns, basset, bore, instrument, clarinet, bore diameter, model, clarinet mouthpiece, operas, basset clarinet, free encyclopedia, mouthpiece, wind, cylindrical bore, B flat, Stephen Fox.

Defination from the web:
basset horn, and the famous 18th century clarinettist Anton Stadler played it. ... He wrote dozens of pieces for basset horn ensembles. ...