20. 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 an item of audio content has not yet been identified; identifying a region of the item of audio content that is preliminarily aligned to the uncertain region in the item of textual content; applying a language model including the text of the uncertain region to the region of the item of audio content to generate a textual transcription of the region of the item of audio content; identifying a significant corresponding word included in both the textual transcription and the text of item of textual content included in the uncertain region; and generating content synchronization information enabling the synchronous presentation of the significant corresponding word in both the item of textual content and the item of audio content.
24. The computer-implemented method of claim 20 further comprising: identifying a substantial acoustic similarity between a first word string of the item of textual content and a second word string of the textual transcription; and identifying a subregion of the item of audio content that corresponds to the first word string; wherein the first word string occurs substantially within the uncertain region in the item of textual content; and wherein the content synchronization information further facilitates the synchronous presentation of the first word string in the item of textual content and the corresponding subregion of the item of audio content.