Re the clarinet:

From
http://www.musicweb-international.com/classrev/2001/may01/Hardy.htm
(worth reading in its entirety):

Of all the great English novelists, with the possible exception of Jane Austen, Thomas Hardy was fondest of music. While Austen enjoyed (and played) art music, Hardy's particular love (while not eschewing art music) was of the music of the people, specifically that of his Dorset youth and earlier. From around 1801 his father and grandfather played stringed instruments in the church band at Stinsford (called "Mellstock" in the novels). Music makes appearances in many of his novels and other writings but particularly in his early novel Under the Greenwood Tree, subtitled The Mellstock Quire, a title Hardy himself preferred. Although it was first published in 1871 it is set perhaps a generation earlier than that and one of its principal plot strands is the replacement of the "Mellstock" church band instruments (here, violins and bass viol, though other bands included flutes, oboes, clarinets, serpents and even brass instruments) and singers - by an organist playing a pipe organ in this case, though many churches acquired barrel organs or, later in the 19th Century, harmoniums.

From The Yetties' website:

Hardy's love of the musical folk of Dorset is beautifully illustrated by this quote from 'Under The Greenwood Tree':



Your brass man is a rafting dog, well and good,

Your reed man is dab hand at stirring ye, well and good,

Your drum man is a rare bowel shaker, good again,

But I don't care who hears me say it

Nothing can spake to your heart with the sweetness of a man of strings