The words that create alliteration in the poem are the following ones: "A big band blares". Alliteration is a stylistic device in which a number of words, have the same first consonant sound and occur close together in a series. In this case, the phoneme is the voiced bilabial plosive phoneme /b/.
Furthermore, alliteration creates a musical effect which makes the literary work pleasing to the ears and easy to remember it by heart.