Definition of instrumency in US English:

instrumency

noun

rare
  • The action or fact of serving as an instrument or means; that which is done or effected by an instrument.

Origin

Mid 17th century. Irregularly from instrument + -cy, after nouns in -ency corresponding to adjectives in -ent.

Pronunciation

instrumency

/ˈɪnstrʊm(ə)nsi/