8. The computer-implemented method of claim 4 , wherein the uncertain region of the item of textual content is identified based at least in part by comparing the uncertain region to an initial transcription of the item of audio content.
4. A computer-implemented method comprising: as implemented by one or more computing devices configured with specific computer-executable instructions, identifying an uncertain region in an item of textual content, wherein the uncertain region includes text of the item of textual content for which corresponding audio in a companion item of audio content has not yet been identified; identifying a region of the companion item of audio content that is preliminarily aligned to the uncertain region in the item of textual content; applying a language model, including text of the uncertain region, to the region of the companion item of audio content to generate a textual transcription of the region of the item of audio; determining that a portion of the textual transcription substantially corresponds to a portion of the text of the item of textual content included within the uncertain region; and generating content synchronization information for synchronizing presentation of the portion of the text of the item of textual content and a portion of the item of audio content corresponding to the portion of the textual transcription.