The music you are listening to is "Se Voi, Lagrime, A Pieno"
by Giulio Romolo Caccini. Caccini's music was modeled
by Claudio Monteverdi as "Seconda prattica". This music was
considered to be the beginning of modern opera, as now poetry could be set
to music with a new, Humanist theory of rhetoric tacens, and not the old,
inflexible, strictly hierarchical Scholastic view of reality.
Standard clef assignments in polyphonic music: "chiavi transported" means
each staff line is a third lower than for standard soprano, alto, tenor
and bass (chiavi naturali). When the clefs are a third higher, this is
called chiavette.