Written-out cadenza from Mozart's K. 398 (end of variation 6) demonstrates the often unmetered quality of cadenzas
Cadenza in Mozart's Violin Concerto K. 271a, III.
In music, a cadenza (from Italian: cadenza[ka'd?ntsa], meaning cadence; plural, cadenze[ka'd?ntse]) is, generically, an improvised or written-out ornamentalpassage played or sung by a soloist or soloists, usually in a "free" rhythmic style, and often allowing virtuosic display. During this time the accompaniment will rest, or sustain a note or chord. Thus an improvised cadenza is indicated in written notation by a fermata in all parts. A cadenza will usually occur over the final or penultimate note in a piece, the lead-in (German: Eingang) or over the final or penultimate note in an important subsection of a piece. It can also be found before a final coda or ritornello.
The term cadenza often refers to a portion of a concerto in which the orchestra stops playing, leaving the soloist to play alone in free time (without a strict, regular pulse) and can be written or improvised, depending on what the composer specifies. Sometimes, the cadenza will include small parts for other instruments besides the soloist; an example is in Sergei Rachmaninoff's Piano Concerto No. 3, where a solo flute, clarinet and horn are used over rippling arpeggios in the piano. The cadenza normally occurs near the end of the first movement, though it can be at any point in a concerto. An example is Tchaikovsky's First Piano Concerto, where in the first five minutes a cadenza is used. The cadenza is usually the most elaborate and virtuosic part that the solo instrument plays during the whole piece. At the end of the cadenza, the orchestra re-enters, and generally finishes off the movement on their own, or, less often, with the solo instrument.
As a vocal flourish
The cadenza was originally, and remains, a vocal flourish improvised by a performer to elaborate a cadence in an aria. It was later used in instrumental music, and soon became a standard part of the concerto. Cadenzas for voice and wind instruments were to be performed in one breath, and they should not use distant keys. Originally, it was improvised in this context as well, but during the 19th century, composers began to write cadenzas out in full. Third parties also wrote cadenzas for works in which it was intended by the composer to be improvised, so the soloist could have a well formed solo that they could practice in advance. Some of these have become so widely played and sung that they are effectively part of the standard repertoire, as is the case with Joseph Joachim's cadenza for Johannes Brahms' Violin Concerto, Beethoven's set of cadenzas for Mozart's Piano Concerto no. 20, and Estelle Liebling's edition of cadenzas for operas such as Donizetti's's La fille du régiment and Lucia di Lammermoor.
Perhaps the most notable deviations from this tendency towards written (or absent) cadenzas are to be found in jazz, most often at the end of a ballad, though cadenzas in this genre are usually brief. Saxophonist John Coltrane, however, usually improvised an extended cadenza when performing "I Want To Talk About You", in which he showcased his predilections for scalar improvisation and multiphonics. The recorded examples of "I Want To Talk About You" (Live at Birdland and Afro Blue Impressions) are approximately 8 minutes in length, with Coltrane's unaccompanied cadenza taking up approximately 3 minutes. More sardonically, jazz critic Martin Williams once described Coltrane's improvisations on "Africa/Brass" as "essentially extended cadenzas to pieces that never get played." Equally noteworthy is saxophonist Sonny Rollins' shorter improvised cadenza at the close of "Three Little Words" (Sonny Rollins on Impulse!).
Cadenzas are also found in instrumental solos with piano or other accompaniment, where they are placed near the beginning or near the end or sometimes in both places (e.g. "The Maid of the Mist," cornet solo by Herbert L. Clarke, or a more modern example: the end of "Think of Me", where Christine Daaé sings a short but involved cadenza, in Andrew Lloyd Webber's The Phantom of the Opera).
Johann Strauss II unusually wrote a cadenza-like solo for cello and flute for the final section of his Emperor Waltz, before a round of trumpets and then the whole orchestra bring the piece to its end.
Beethoven's "Emperor" Concerto contains a notated cadenza. It begins with a cadenza that is partly accompanied by the orchestra. Later in the first movement, the composer specifies that the soloist should play the music that is written out in the score, and not add a cadenza on one's own.
Tchaikovsky's first piano concerto is notable not only for having a cadenza within the first few minutes of the first movement, but also for having a second - substantially longer - cadenza in a more conventional place, near the end of the movement.
Rachmaninoff's Piano Concerto No. 3, in which the first movement features a long and incredibly difficult toccata-like cadenza with an even longer alternative or ossia cadenza written in a heavier chordal style. Both cadenzas lead to an identical section with arpeggios in the piano and a solo flute accompanying, before the cadenza ends quietly.
Carlos Chávez's Violin Concerto has a seven-minute unaccompanied cadenza as the third of its five main sections, despite the fact that the soloist plays almost without a break throughout the rest of the 35-minute-long composition
Composers who have written cadenzas for other performers in works not their own include: