Figured bass was basically a chord chart (also indicating the
inversion ) in the Baroque period and musicians improvised upon
those charts much like jazz players do today using modern chord
chart notation. It was during the later classical period that
composers started writing music down in an exact manner and
expected musicians to play exactly note by note. Also, figured bass
is similar to the Nashville number system. I is the tonic and V is
the dominant.....et cetera.