where does the cadenza usually occur in a concerto
Cadenza 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.
String section The string section is the largest body of a single instrument category in the standard Classical orchestra. It normally consists of the first violins, the second violins, the violas, the cellos, and the double basses (or basses). The first and second violinists play the same types of instruments; the difference between the two sections is in the types of musical lines that are typically given to each section. The first violins are generally given the melody or higher-pitch musical lines, whereas the second violins generally play a part that is lower in pitch than the first violins. The second violins may play a harmony part, a countermelody or an accompaniment passage. In discussions of the instrumentation of a musical work, the phrase "the strings" or "and strings" is used to indicate a string section as just defined. An orchestra consisting solely of a string section is called a string orchestra. Smaller string sections are used in jazz, pop and rock music arrangements and in musical theatre pit orchestras.