Part Four, covering the period 1810-1815, was a crucial one for Southey’s career and reputation. It has, however, never before been fully documented or fully understood. By 1810 he was established in Keswick...
237. Robert Bloomfield to James Montgomery, 26 May 1809*
London, May 26. 1809
Upbraid me not, if you can help it, for my extreme tardiness. I have had some of the world's cares to buffet with,—a long and severe rheumatic winter, and a total privation of the strength and resolution to attend to music or poetry;—add to this, my son with a broken leg, which, considering it was that which had been long lame, and must continue so, has been as far restored as reason could crave. He is well, and his father is alive again.
You know the nature of the instrument I send, and therefore I only observe, that if when placed under the lifted sash, or just inside, so as to conduct a current of air through the strings, it should not play satisfactorily, then take off the top board and place the harp alone on the broadest edge with the strings rising nearly perpendicularly over each other, and close to an inlet made by lifting the sash about an inch. I have no doubt that it will perform; but I should be glad to hear of any intimations to that effect, at any convenient time. I have been informed that you too have been out of health, or spirits, or both,—I know not which, but hope to hear a good account.
Your harp, I doubt, is too short to admit of larger strings; but you may possibly enjoy quite as much the extreme softness of the smaller ones: that you may, is my hope: and that you may find some amusement from a thing so frail, and not suffer it to be a 'Harp of Sorrow,'  is my ardent desire. What is your Muse about? will not this delightful season set you a-going again? Whether it does, or not, I remain, Sir,
Your humble servant,
 Bloomfield alludes to Montgomery's 1807 poem 'The Harp of Sorrow':