A new report from The Washington Post outlines a tool that lets the NSA record every phone call in a country for a entire month, then replays entire conversations as needed. Think of it like a DVR of every conversation that occurs over a rolling 30-day period — including any conversations involving Americans.
The retrieval tool is called RETRO, building off of a voice call collection program called MYSTIC that was introduced in 2009. According to the Post report, written by Barton Gellman and Ashkan Soltani, which combines confidential interviews with documents leaked by Edward Snowden, RETRO went into operation against an unidentified country in 2011. In other words: this program, unlikely many others, belongs solely to President Obama.
It appears to work like this. Once turned on, MYSTIC scoops up the call data — including voice data — and throws it into RETRO. Analysts can then "retrieve audio of interest that was not tasked at the time of the original call" from RETRO — meaning that they can listen to calls that weren't analyzed in real-time. (Note: it's not actually a DVR. There's no video. It's an analogy.) "Each month" analysts use RETRO to "send millions of voice clippings, or 'cuts,' for processing and long-term storage." After 30 days, content drops out of the tool, constantly being replaced by new information.