The form of Elizabeth Barrett Browning's "A Musical Instrument" is fairly conventional. The poem consists of seven six-line stanzas, each of which has a regular rhyme scheme, abaccb. This gives a certain repetitive quality to the verse, which in some respects could be said to reflect the monotony of the poet's life as a disabled woman in Victorian Britain.

Also, one must bear in mind that Barrett Browning is consciously drawing upon classical mythology in the poem—the story of Pan—so it is entirely appropriate in this context to use a conventional form. In doing so, the poet is establishing a connection between herself and the masters of verse of the ancient world.

As far as the theme of "A Musical Instrument" is concerned, one could say that it deals with the possibility of creating great art out of almost nothing. In the poem, the demigod Pan somehow manages to create music that is "Sweet, sweet, sweet" out of a humble reed.

By the same token, Elizabeth Barrett Browning, a woman living at a time when women were actively discouraged from engaging in literary pursuits, has created a work of art, a poem, despite the many obstacles she has to face, both as a woman and as someone with a serious disability.