This fine recording is courtesy of Zero Hedge and The Internet Archive. It is a recording of market maker activity from the S&P 500 futures trading pit during last year's "flash crash". Futures prices plummeted, then soared back up again, probably due to algorithmic trading, although the event remains the subject of investigation by the U.S. Securities and Exchange Commission, among others.
This is one of the most dramatic audios I've ever heard. It is approximately eleven minutes in length, audio only. It was recorded in the S&P index futures pit on 6 May 2010, when the DJIA crashed by nearly 1000 points in 20 minutes.
More on the Flash crash from The Slope of Hope Wiki
The Slope of Hope Wiki is part of The Slope of Hope website. It is run by Tim Knight whose very first stock trade was on October 19, 1987, or Black Monday.
Tim Knight is a permabear. I have a strong ursine tendency too, so that is (partly?) why I like reading Zero Hedge.