What Is a Cadenza? The Moment the Orchestra Stops and the Soloist Doesn't

The standard placement is near the end of a first movement, at a point where the harmony has arrived on a chord that demands resolution and the orchestra stops rather than resolving it. That suspension is what licenses the passage, since the listener knows a resolution is owed and everything the soloist plays is heard as a delay of it. The soloist typically works through material from the movement, displays technique, and eventually signals the end with a long trill over the unresolved harmony, at which point the orchestra re-enters and the resolution finally arrives. The convention is remarkably stable across the concerto repertoire, and its logic is the same as a pedal point at larger scale, since the entire passage is held in suspension by a harmony that has not been allowed to move. Slow movements and finales also contain them, generally shorter.

The history of the passage tracks a broader change in what performers were expected to do:

• •In the eighteenth century the soloist improvised it, and composers wrote only a pause and a figure indicating where it went
• •Composers who performed their own works improvised theirs and sometimes wrote them down afterwards, which is how several famous examples survive
• •Beethoven wrote out the cadenza in his final piano concerto and instructed that it not be replaced, which is the usual marker for the change
• •Nineteenth-century composers increasingly wrote them in, integrating them into the structure rather than leaving a gap
• •Performers meanwhile composed cadenzas for earlier concertos, and several of those became standard and are still played
• •The twentieth century brought both scholarly reconstruction of period improvisation and newly composed cadenzas in modern idioms

Composers and performers writing these passages face a real compositional problem, since the passage has to sound spontaneous while being coherent. The conventional solution takes themes from the movement and treats them in ways the movement did not, putting a lyrical theme into a virtuosic texture, combining themes that never met, or moving a fragment through distant keys, which gives the passage material the listener recognises and an argument the movement did not make. Proportion matters, since a passage long enough to lose the sense of suspension undoes its own reason for existing, and the best examples are shorter than performers tend to want. Ending matters most, since the trill and the orchestral re-entry are the point the entire passage has been delaying, and a weak approach to it wastes everything preceding. Cadenzas written by later composers for earlier concertos also face a stylistic question, since matching the original period and writing in a contemporary idiom are both defensible and produce completely different results.

The shift from improvisation to composition changed the meaning of the passage substantially. Improvised cadenzas were genuinely unpredictable, different at every performance, and audiences attended partly for that, which made the concert an event rather than a reproduction. The soloist demonstrated musicianship rather than only technique, since inventing convincing material under pressure requires understanding the piece rather than only having practised it. What was gained by writing them down was quality control and integration, since a composed cadenza can develop the movement's material properly and fit its proportions, and the historical record of improvised examples includes a great deal that was merely showy. The current situation is mixed, with most performers playing established cadenzas, a minority improvising, and a growing interest in the practice among players working in historical performance. The debate is really about whether a concert reproduces a work or presents an occasion.

Unaccompanied solo passages with the same function appear well outside the concerto. Opera has its own tradition of elaborate vocal display over a suspended harmony, and the conventions for where singers added ornamentation were as established as the instrumental ones and are similarly reconstructed today. Jazz solos occupy comparable territory in a different way, since they are improvised over a structure and are expected to be different every time, which preserves the practice the classical tradition largely abandoned, though the harmonic suspension works differently. Organ improvisation survived as a living skill in church practice long after it faded elsewhere, and organists are still trained in it. Folk and traditional musics never made the separation between composer and performer that produced the problem in the first place. The classical concerto is therefore the unusual case, having had improvisation as a central expectation and then removed it.

The orchestra stops on a chord that demands resolution, and everything the soloist then plays is heard as a delay of it, ending with a trill that brings the orchestra back. It was improvised through the eighteenth century and written down afterwards, with Beethoven's instruction not to replace his the usual marker. Writing them down bought integration and quality and lost the unpredictability audiences came for.