By the early 18th century, the Baroque prelude was often a piece of music which was followed by a fugue. Johann Sebastian Bach wrote lots of pieces like this, which were called “Preludes and Fugues”. Most of them were for keyboard instruments such as the harpsichord or organ. Forty-eight of them are from a collection called "The Well-Tempered Clavier", which was made up of two sets of twenty-four preludes and fugues that are each written in a different major or minor key signature. The first prelude, in C major, is very famous. It sounds like an improvisation made up of gentle broken chords like a lutenist might play. (This is the piece that Charles Gounod later used for his "Ave Maria".) Preludes were also pieces which were followed by a series of dance movements (a “suite”).