Some composers, such as Berlioz, really went all-out writing for huge orchestras.
Instrument design and construction got better and better, making new instruments such as the piccolo and the tuba available for orchestras.
They meant for the parts to be played by whatever was around.
But around 1600 in Italy, the composer Claudio Monteverdi liked things just so.
Composers began to write for the specific instrument they had in mind.
This meant knowing each instrument's individual "language" and knowing what kind of music would sound best and play easiest on a particular instrument.
Wagner went so far as to have a new instrument, the Wagner Tuba, designed and built to make certain special sounds in his opera orchestra.
In one of his symphonies, Strauss wrote a part for an alphorn, a wooden folk instrument up to 12 feet long!
Prometheus was the last of the Titans in Greek mythology.
He sided with the younger upstart gods, led by Zeus, in their war against the Titans.