Claudio Monteverdi was essentially the first modern composer. His was a sharp dividing line between renaissance style music - really only heard these days as a curiosity - and what we still hear regularly as "normal" (albeit "highbrow") music.
His music was revolutionary, in that it gave birth to new and long lasting forms. This piece is the oldest surviving opera that is still performed. The face that it survived while a few older did not tells us what people at the time thought of its value. That it's still performed today tells us what contemporaries think of its value.
It was also the birth of the Baroque stye - a twofer of musical genius, if you will.
Claudio Monteverdi was born on this day in 1567. Opera was born a few years later in in 1607 when he wrote this piece.