A composition (usually in symphonic form with three movements) in which one instrument (or two or three) stands out in bold relief against the orchestra, or accompaniment, so as to display its qualities or the performer's skill.
The cello is a hero because of its register - its tenor voice. It is a masculine instrument, whereas the violin is feminine because of its soprano pitch. When the cello enters in the Dvorak Concerto, it is like a great orator. Mstislav Rostropovich