How the NSA Converts Spoken Words Into Searchable Text

Presto Vivace writes: Dan Froomkin reports at The Intercept: "Though perfect transcription of natural conversation apparently remains the Intelligence Community's 'holy grail,' the Snowden documents describe extensive use of keyword searching as well as computer programs designed to analyze and 'extract' the content of voice conversations, and even use sophisticated algorithms to flag conversations of interest." I am torn between admiration of the technical brilliance of building software like this and horror as to how it is being used. It can't just be my brother and me who like to salt all phone conversations with interesting keywords.