Figured bass

The short hand way of describing the harmony in the Baroque era. Briefly, the absence of a figure underneath the bass line implies a root position chord, whereas, 6 implies a first inversion, 7 implies a (root position) seventh chord,  # implies a major third, and an oblique stroke through a numeral means that the note is chromatically sharpened, etc. Figured bass has a good deal of room for improvisation within the framework set by the composer. One can play simple chords with a variety of spacing, introduce passing notes, or incorporate melodic motifs in imitation of the treble or bass parts.