Insertion aria

An insertion aria (aria di baule in Italian, also known as suitcase aria, interpolated aria, or trunk aria) is an aria sung in an opera for which it was not composed. It was a practice that began in the seventeenth century and continued actively through the late 19th century and sporadically through the 20th century. The insertion aria could replace an existing aria, or might be added to an opera. All insertions were planned in advance.