Italy is a natural geographic unit bounded by the Mediterranean Sea on three sides and the Alps to the north. Politically it was united under the ancient Roman Empire, then for centuries it was a divided collection of separate city-states, many dominated by foreign powers. It was eventually re-united in the Risorgimento of the 1860s with Cavour in the north and Garibaldi in the south.
Plainsong was the only form of church music in the early Middle Ages, and this was passed on by oral tradition Pope Gregory is reputed to have imposed order and discipline to the plainsong, and so it is now usually called Gregorian Chant. The beginnings of musical notation as we know it today were documented by Guido D'Arezzo around 995 AD.
Italy became an important centre for European music in the renaissance of the 16th century, Palestrina and Allegri being pre-eminent in church music, Monteverdi in opera. In the baroque, Vivaldi, Corelli, Scarlatti are renowned composers. Opera dominated Italian musical culture in the classical and romantic periods, so many talented composers and instrument-makers sought their fortunes in other parts of Europe. Clementi went to London, Boccherini went to Madrid.
Rossini, Verdi and Puccini are pre-eminent in the field of Italian 19th century opera, and Respighi broke with Italian traditions and wrote richly orchestrated instrumental music, greatly influenced by the French Impressionist Debussy.