Rhyme is the sound device most recognized by the general public. In rhymed poems divided into couplets, the last word in the two lines of each verse will sound the same except for the beginning letter. In poems with stanzas, the same two lines typically will end in rhymes in each verse, but the pattern can vary greatly. Repetition is another sound device used for emphasis. An example is the Robert Frost poem, "Stopping By Woods On A Snowy Evening. The last two lines are the same: "And miles to go before I sleep, And miles to go before I sleep."
Alliteration refers to repeated consonant sounds of stressed syllables placed close together in a line or verse, such as Robert Frost's passage, "dawn goes down to day." Alliteration depends on sound rather than spelling, so cat and cease are not alliterative even though they both begin with the same letter. Chaparral Poets warns that this is an obvious device and should be employed with restraint, except perhaps in more frivolous poetic forms like limericks and humorous verse.
Vowel sounds repeated in neighboring words is called assonance. These should occur in stressed syllables. John Keats used assonance to good effect in this line: "Thou foster child of silence and slow time." The long "i" of child is repeated in silence and time.
Consonance is a repetition of sounds in nearby words, but this time consonants are highlighted. This device differs from alliteration because the like consonants do not have to be at the beginning of words. The "t's" in "boats into the past" are an example of consonance.
In this device, words imitate the sound they represent. Many action words fall into this category: hiss, clang, murmur, gush, crackle, sizzle. Listening to the line "Hear the steady tick of the old hall clock," you understand that tick contributes to the sensory sound, as well as the meaning, and the line also contains the consonance of the "ck" in tick and clock.