1. A concept-service component of a content-search-service system for searching a content item having an audio track, the concept-service component comprising: a hardware processor configured to: receive, as input, a content ID and search query, wherein the content ID uniquely identifies the content item; use the content ID to retrieve a category ID, ontology, vocabulary, and a transcript, wherein: the category ID relates to a subject matter of the content item, and the transcript includes a textual rendering of the audio track; receive a search query and corrects and linguistically normalizes terms or phrases within the search query; and use the linguistically normalized terms and phrases to process the transcript to assign ontology-based scores to terms or phrases in the transcript using a transcript scorer; and a memory coupled with the processor, wherein the transcript scorer: prepares a list of term/ontology-metric pairs for each term or phrase in the linguistically normalized terms or phrases of the search query; and for each term or phrase in the transcript, associates a score with the term or phrase based on co-occurrence-metrics in the prepared lists of term/ontology-metric pairs, and wherein the transcript-scorer prepares a list of term/ontology-metric pairs for each term or phrase in the linguistically normalized terms or phrases of the search query by: identifying each entry in the ontology that includes the term or phrase paired with a second term; and for each identified entry, computing a co-occurrence metric as a combination of the co-occurrence values in the identified entry, and adding an entry to the list that includes the second term and the computed co-occurrence metric; and adding an entry to the list that includes the term and an identical-term co-occurrence metric.