Ten experts decide who and what changed the course of music history.

The most important innovation of the late 18th and early 19th century was the refinement, development and popularity of the piano. First invented by Cristofori around 1700 – who single-handedly solved some of the technical challenges of a hammered keyboard – the piano didn’t catch on until later. Mozart didn’t play a piano with hammers until he was 21 and Haydn was in his late 40s when he came across the new-fangled Viennese instruments of the 1780s. Piano and harpsichord coexisted for a while. In 1774 an English amateur compared the two: “If the pianoforte has deficits which a good harpsichord has not, it has beauties and delicacies which amply compensate, and which make the harpsichord wonderfully flashy and insipid when played after it… There are times when one’s ear calls only for harmony and a pleasant jingle… but as soon as ever my heartstrings catch the gentlest vibration, I swivel me round incontinently to the pianoforte.” But by the late 18th century, people “found the scratching of the quill of the harpsichord intolerable”.

The piano underwent drastic changes in the 19th century. More and more keys...