These are the chords I've found. It's best to sing the flat 7. against the G before going to the Dm chord.

G                                     F                   C            G
Open the door softly, I've something to tell you, dear.
G                                           Dm       Am      G
Open it up no widerthan the crack upon the floor.
G             Em   G            F                     C          G
Open the door softly,I've something to tell you, dear.

Warm summer grasses have whispered it in your ear.
Skeins of shining water ask you patiently to hear.
Tall lonely timbers have taught it to the deer.

Sad winds in autumn will tell you as they pass by.
Wild geese flying eastward leave their music in the sky.
Listen at evening, and answer the wild birds' cry.