That said, the score does not provide complete and exact instructions on how to perform a historical work. Even if the tempo is written with an Italian instruction (e.g., Allegro), we do not know exactly how fast the piece should be played. As well, in the Baroque era, many works that were designed for basso continuo accompaniment do not specify which instruments should play the accompaniment or exactly how the chordal instrument (harpsichord, lute, etc.) should play the chords, which are not notated in the part (only a figured bass symbol beneath the bass part is used to guide the chord-playing performer). The performer and/or the conductor have a range of options for musical expression and interpretation of a scored piece, including the phrasing of melodies, the time taken during fermatas (held notes) or pauses, and the use (or choice not to use) of effects such as vibrato or glissando (these effects are possible on various stringed, brass and woodwind instruments and with the human voice).
The score does not provide complete and exact instruction on how to do what?
perform a historical work