How we cite our quotes:
I love to listen to the hollow sighs (3)
The speaker has odd taste, to say the least. She doesn't like listening to birds singing or the river babbling. Nope, she likes listening to the sighing of the wind. And these aren't just any sighs. They're hollow sighs. So the sighs are empty and devoid of meaning. This is one mopey speaker!
Strange sounds are heard, and mournful melodies,
As of night wanderers, who their woes bewail! (7-8)
The speaker imagines that she can hear funny music on the wind, ghostly music. And check out all the alliteration in these lines: the repeated S of "strange sounds," the repeated M of "mournful melodies," and the repeated W of "wanderers who their woes bewail." Those letters in particular make a kind of windy, sighing sound. Appropriate for ghostly music, don't ya think?
Here, by his native stream, at such an hour,
Pity's own Otway I methinks could meet,
And hear his deep sighs swell the sadden'd wind! (9-11)
The speaker imagines that she could meet the ghost of the poet Thomas Otway, since he grew up around these parts. What would the ghost of Thomas Otway be doing down by the river, anyway? What do all good poets do when they're down by the river? They sigh and feel melancholy, obviously.