(It.: ‘open’, ‘clear’, ‘frank’, ‘bold’, ‘plain’).
In medieval music, particularly in the Estampie but also in the Ductia and in many song forms, aperto and chiuso are used in the same sense as the modern words ‘prima volta’ and ‘seconda volta’. Normally the open ending (aperto) was on a less final pitch than the closed ending.
DAVID FALLOWS