cadenza

A concerto is a large piece for an instrumental soloist (usually playing piano or violin) and orchestra. Concertos are often extremely demanding for the soloist, but the most difficult part of all may be the cadenza, when the orchestra drops out completely, leaving the soloist to dazzle the audience with a set of flourishes, often completely original, right before a movement ends. Cadenzas are also heard in many vocal arias, especially those of the 18th century. The word, borrowed from Italian, originally meant "cadence;" thus, the cadenza, even if it lasts for a couple of minutes, is essentially a decoration of the final important harmonic cadence of the piece.