Who was Niccolo Paganini?
A famous Italian violinist, regarded as a virtuoso of the instrument. In addition to being a child prodigy, he pioneered some new playing techniques (double stops, expanded use of harmonics) and composed a few pieces for violin himself. He lived in the early 19th century.
There is a wonderful story about Paganini which I cannot substantiate, but which ought to be true if it is not. He was amazingly creative when it came to technique, as explained above. Many large-scale pieces for soloists (concertos) include extended passages where the soloist will play alone, and perform an extended cadenza showing the soloist's technical skills. Originally these cadenzas were often written by the individual performer and not necessarily 'scored' by the composer. When Paganini would rehearse with orchestras in preparation for concerts, the violinists would stop cold at the time that Paganini's cadenza was to be inserted, and focused on him, hoping to catch some ideas about what he was doing, and how. More often than not, Paganini would play just a few notes, turn to the conductor, and say "et cetera", indicating that he was saving the real thing for the concert. No free lessons!