[Published in part (lines 7-24) by Medwin (under the title, "An Ariette for Music. To a Lady singing to her Accompaniment on the Guitar"), "The Athenaeum", November 17, 1832; reprinted by Mrs. Shelley, "Poetical Works", 1839, 1st edition. Republished in full (under the title, To —.), "Poetical Works", 1839, 2nd edition. The Trelawny manuscript is headed "To Jane". Mr. C.W. Frederickson of Brooklyn possesses a transcript in an unknown hand.]
1.
The keen stars were twinkling,
And the fair moon was rising among them,
Dear Jane!
The guitar was tinkling,
But the notes were not sweet till you sung them
Again.
An exclamatory statement of love that needs no explanation. Shelley, who is capable of highly complex writing, for example in  Sonnet to Byron  seems capable also of the most straightforward, easy-to-understand love poetry, falling back as he does on traditional language and imagery. 

To Jane: The Keen Stars Were Twinkling