Cadenza
Solo insertion with virtuoso improvisation.
What it means
A cadenza is a solo section within a concerto movement or an aria in which the orchestra falls silent and the soloist plays or sings alone. Its traditional place is shortly before the end, where the harmony pauses on a six-four chord; from there the cadenza finally leads back to the closing cadence, often announced by a long trill. Historically it was improvised; since the nineteenth century, composers have often written it out.
In the notation
In older scores, at the spot in question there is a fermata over the chord and the word itself or nothing at all; the rest is up to the soloist. Written-out cadenzas appear as an inserted section, often without bar lines or with small notes. Numerous works exist with cadenzas by different authors.
Musical use
The cadenza combines two things: a demonstration of the soloist's skill and a summing-up of the movement. Good cadenzas take up thematic material and shed new light on it instead of merely stringing together runs. Because it stops the orchestra, it acts like a suspension of time, out of which the music finds its way back into the ending. In opera, the ornamented closing cadence of an aria corresponds to it. In music after 1800 the section sometimes migrates to other places in the movement or is integrated entirely into the course of the piece.
Performance practice
Choose or write a cadenza that fits the style of the work — length, harmony, and technique should not come from a later era. Work with the thematic material of the movement. Keep the connection to the ending clear: the trill and the orchestra's entry must be prepared unmistakably. Practise the cadenza in context with the end of the movement, not in isolation. In rehearsal, settle the cue for the orchestra's re-entry.
Bear in mind that the length must fit the design of the movement: a cadenza that exceeds the movement in scale shifts the proportions. Keep it shorter than seems tempting. In works with a written-out cadenza, check whether it comes from the composer; otherwise the choice is free.