Synonyms for Sestet (same or very similar meaning)
WordNet sense 1 (the cardinal number that is the sum of five and one):
sextet, sextuplet, six, hexad, sise, sixer, VI, Captain Hicks, half a dozen
WordNet sense 2 (six performers or singers who perform together):
sextette
From the ODE community, based on WordNet
add/edit