These are different problems. The written (or more accurately, typed)* word is an inherently symbolic representation. Recorded audio (PCM WAV or similar) is no

These are different problems. The written (or more accurately, typed)* word is an inherently symbolic representation. Recorded audio (PCM WAV or similar) is not. The format itself doesn't encode meaning about the structure. The written word is more akin to MIDI, which can exactly represent melody, but cannot exactly represent sound. MP3 is a weird halfway house, it's somewhat symbolic in terms of using wavelets to recreate a likeness of the original sound, but the symbols aren't derived from or directly related to the artist's original intent. * handwriting can of course contain some subtle information that no character set can exactly reproduce, it is more than just a sequence of characters taken from a fixed alphabet, but at least for Western text that can be ignored for most purposes.