Purpling the landscape, far and wide,
On the dark promontory's side
I'll gather wild flow'rs, dew besprent,
And weave a crown for THEE,
GENIUS OF HEAV'N-TAUGHT POESY!
While, op'ning to my wond'ring eyes,
Thou bidst a new creation rise,
I'll raptur'd trace the circling bounds,
Of thy RICH PARADISE extended,
And listen to the varying sounds
Of winds, and foaming torrents blended.
And now, with lofty tones inviting,
Thy NYMPH, her dulcimer swift smiting,
Shall wake me in ecstatic measures!
Far, far remov'd from mortal pleasures!
In cadence rich, in cadence strong,
Proving the wondrous witcheries of song!
This line refers to the dulcimer that Robinson and Coleridge both refer to. This is a string instrument that resembles a violin. She is trying to describe how beautiful this sound is and how she enjoys it so much listening to it in the middle of the night. 

To the Poet Coleridge