Baroque music
Baroque music was often a melody with a bass line at the bottom. This could be, for example, a singer and a cello. There was also a harpsichord or organ that played the bass line as well, and made up chords in between. Often the composer did not bother to write out all the chords (harmonies) but just showed some of the chords by figures, leaving it to the performer to decide exactly which notes to play. This is called “figured bass” or “basso continuo”. The soloist, who played or sang the melody on top, often put in lots of ornamental notes. Again: the composer did not write this all down but left it to the performer to improvise something nice around the notes he had written.