One of the most important elements of poetry, is voice. Although voice is distinct, it isn’t as easy to pin-down as other elements of poetry. Unlike alliteration and rhyme, voice is not one thing. Voice is made up of many elements and always differs from poet to poet. Think of the different audible voices in the world—mine sounds different than yours, and yours different from someone else's. The everyday voice we speak in is our primary voice.
For poets, it is necessary to understand the difference between primary voice and poem specific voice. The difference between these two, is that primary voice is consistently present throughout a poet’s work— it is the poet’s everyday voice, the voice they primarily write in. Apoem specific voice is a voice that occurs on occasion. It is usually used to create a specific effect. Voice of an imaginary person, voice of a personified object, or voice of an abstraction can be poem specific voice. In other words, it is not the primary voice of the poet, although it is still one of their many voices.
With this said, it is important to note that primary voice and poem specific voice can mix. Even though I might mimic Forrest Gump (poem specific voice), you might detect that it is me because you are familiar with my primary voice. Yes, I might sound like Forrest Gump, but there are hints of my own voice bleeding through. This is also true in poetry, and is often why identifying primary voice within a poem mixed with poem specific voice, can be difficult if one is not familiar with a particular poet.