Pipe organ
No other instrument has developed in such a wide variety of ways as the organ. If Bach, who lived in the early 18th century, had gone from his home in Germany to France, he would have found it impossible to play his music properly on French organs. If Couperin, who lived at the same time, had gone from his home in France to Germany, he would not have been able to play his music on the organs that Bach was using. Neither of them could possibly have played on an organ in England at the time. For one thing, English organs in the 18th century still had no pedals. This means that organists need to know a lot about what organs were like in other countries in other centuries in order to know what registrations to use when playing music by composers of the past.