One of the major problems in the performance of a classical concerto such as the Mozart Oboe Concerto (K. 314) or any of the other wind concertos of the period is caused by the absence of music for the cadenzas. The performer of the period was expected to extemporize a cadenza which had spontaneity and also exhibited the craft of a composer-performer. The following account of the performance-practice is given by Abraham Veinus.
With such composer-performers as Mozart and Beethoven, the cadenza reached its height as a medium for spontaneous improvisation. The fame of their extempore renditions has come down to us from more than one wonder-struck observer, and one needs only to remember the profound sincerity of their music to conjecture with reasonable certainty that their cadenza improvisations were aflame with creative fire and controlled by a stupendous knowledge of the craft of composition. [Abraham Veinus, The Concerto (New York: Dover Publications, 1964), pp. 40-41.]
The modern performer, not often a composer, usually relies on inept, out-of-style and overly-lengthy cadenzas which contribute little to the form of the piece. This practice is severely criticized by Veinus,
The composition of cadenzas for Mozart and Beethoven concertos has been entrusted, in consequence, to virtuosi or distinguished pedagogues who understand how to write brilliantly for their special instrument, but who do not necessarily understand, as the composer did, how to write music. According to modern concert-hall practice, the cadenza may now be defined as that part of the concerto where the orchestra stops playing and the listener, to all intents and purposes, stops listening, so that all and sundry may concentrate upon the bag of tricks which the performer as wizard-virtuoso (not as a maker of music) is to trot out for inspection.
and also by Hutchings in regard to the Mozart piano concertos:
It must be stressed in regard to Mozart's cadenzas, not so much that they are but embellishments-protracted cadences-like those made by singers in arias of the period, but that to intrude something highly organized and climactic into a highly organized movement is to nurture a weeping tumour. All too frequently we console ourselves with the thought that, since the movement is almost finished, we have heard Mozart and are aware of his general design, so that we can settle down to ten minutes of Hummel, Tausig; Reinecke, or Sekles.[Arthur Hutchings, A Companion to Mozart's Piano Concertos (London: Oxford University Press, 1950), pp. 205-206.]
The expansion of the final cadence of the concerto movement grows out of earlier performance practice. Again, quoting Veinus:
The habit of expanding a cadence into a brief coloratura cadenza can be traced back to folk sources . . .[Veinus, The Concerto]
Performers of Baroque music can show a large number of examples calling for improvised cadenza expansion.
From the standpoint of musical form, the cadenza of the classical period is a harmonic expansion between the tonic six-four chord and the dominant five-three chord of the final authentic cadence of the movement proper. This cadence is usually followed by a short coda or, as in the first movement of the Mozart Oboe Concerto, by a series of codettas.
Fortunately, Mozart left a number of composed cadenzas to his piano concertos which Hutchings recommends be used as models by the modern performer for the composition of stylistic cadenzas to the classical concertos to which none have been provided by the composer.
Mozart's own cadenzas should be played where they are available, and should be models when they are not available.
In the opinion of Veinus, these models were written out for friends and pupils. What better friend or teacher to have than a Mozart!
Furthermore, the cadenzas which Mozart did write out were intended less for himself than for friends and pupils.[Veinus, The Concerto ]
These model cadenzas of Mozart are listed as Mozart: (K.624) Thirty-five Cadenzas to his Pianoforte Concertos and are available in an inexpensive form in Kalmus Study Score, No. 988; W. A. Mozart, Minor Pieces for the Piano, (pp. 62-101).
A scanning of these cadenza models will at once reveal that, as in the words of Hutchings,
. . .they are slight, often brilliant, and usually, though not invariably, make reference to a theme or themes. There is never any elaborate counterpoint or structure, and the theme chosen for a starting-point is rarely the chief one, or one which has been played in the preceding ritornello. One quality is invariable-brevity. [Hutchings, A Companion]
In order to use any one of these cadenzas as a model for the composition of a cadenza for a classical concerto, a first step should be a melodic and harmonic analysis of the model. The choice of Cadenza No. 15 to the Piano Concerto in C Major (K.415) as a model for the composition of a cadenza for the first movement of the Oboe Concerto is threefold.
Observations which can be made on the basis of this analysis are:
Using this analysis as a model, the following is the author's cadenza composition for the first movement of the Mozart Oboe Concerto.
The above cadenza has a similar melodic and harmonic analysis to the Mozart model, as shown below in Figure 6.
If the composition of cadenzas for classical concertos generally follows the analysis of a model cadenza and if the new cadenza can "hold up" to the same analysis, then the performer can once again be performer-composer and provide his or her performance of the classical concertos with authenticity by including in that performance a cadenza which has been personally composed with knowledgeable and stylistic craftsmanship.