Sound of a Failing Universal Joint

This sound was coming from a failed universal joint (front u-joint). Complete mechanical failure was likely imminent.
We threw in new Spicer universal joints and she drives as quiet as can be now.
This is on a 1964 Ford Thunderbird but pretty much any car with a Hotchkiss style driveline may experience a similar issue eventually.
A failed front u-joint can be very dangerous and cause a lot of damage if it lets loose. It’s a very cheap fix and easy to do with a small shop/arbor press.