Audio is unnecessary. The video shows a slow-motion decoding of a gzipped version of the poem. The red text between brackets is a chunk of text that was earlier stored into the huffman tree (example "W{hile I }" means that the "hile I" was previously encoded; it occurred in the substring "while I pondered"). You can see the red chunks quickly occupy the larger volume of the poem, which visually highlights the symmetry in lyric that the computer is using to encode the file as gzip.
(Its not a Huffman tree. When you replace a fragment with a reference to previous content, its termed 'dictionary coding'. Huffman trees are what you use for `entropy coding`, which is how you compress the bits you didn't zap with the dictionary.)
Pretty neat.