it is difficult to say when the orchestra was invented because instruments have played together for many centuries. if we say that an orchestra is a group of string instruments with several players playing the same part, and that there may be wind instruments (i.e. woodwind and brass) or percussion playing as well, then the 17th century is the time that orchestras started. in paris in 1626 king louis xiii had an orchestra of 24 violins (called "24 violons du roi"). later in the century the english king charles ii wanted to be like the french king and so he, too, had a string orchestra. gradually the other instruments were added. at this time there was usually someone playing the harpsichord (the continuo part). it was often the composer himself, who would have conducted from the keyboard at important moments like the beginning and end of the piece.