WordRel.com

• a musical composition for two performers

  synonym	duetduette
  hypernym	compositionmusical compositionopuspiecepiece of music
  mero part	primosecondo

• a pair who associate with one another

  synonym	coupleduettwosome
  hypernym	pair
  hyponym	same-sex marriage

• two performers or singers who perform together

  synonym	duetduette
  hypernym	musical groupmusical organisationmusical organization
  instance hyponym	Laurel and Hardy

• two items of the same kind

  synonym	bracecouplecoupletdistichduadduetdyadpairspantwaintwosomeyoke
  hypernym	2deuceIItwo
  hyponym	doubleton
  mero part	fellowmate