Read the passage from "Ode on a Grecian Urn."

Heard melodies are sweet, but those unheard
Are sweeter; therefore, ye soft pipes, play on;
Not to the sensual ear, but, more endear'd,
Pipe to the spirit ditties of no tone

Keats uses the phrase "spirit ditties" to describe the

music the gods on the urn favor the most.
songs the people on the urn appear to be playing.
music created by blowing across the top of the urn.
songs that were popular at the time the urn was made.