when you're going fast enough the whole rigging will start howling as they get vibrated like big violin/bass/piano wires

on a beachcat it's because you are cutting through the air fast enough to get them oscillating, on the old square riggers it was because you were caught out in hurricane winds...

http://www.google.com/search?q=wind+howling+through+the+rigging&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-GB:official&client=firefox-a