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when do cadenzas usually occur in solo concertos
The cadenza normally occurs near the end of the first movement, though it can be at any point in a concerto.
what is the music definition of candenza
A cadenza is an improvised or written-out ornamental passage played or sung by a soloist or soloists, usually in a free rhythmic style, and often allowing virtuosic display.

Question: what are the greatest examples
Self-contained rewrite: what are the greatest examples of a candenza