Period instruments
Musical instruments have changed a lot during the last few centuries.  Composers like Johann Sebastian Bach (1685-1750) wrote music for instruments which sounded differently from the way they do today.  Although most of the orchestral instruments we use nowadays were already in use in Bach’s day, instrument makers have made changes to them.  These changes often gave the instruments a bigger sound so that they could be heard well in large concert halls.  Orchestras also have increased in size.