The March 1956 recording of Ginsberg reading Howl in Berkeley, it turns out, was not the first tape of it made. A month earlier AG and Gary Snyder had hitched up to Reed College (Snyder has grown up in Portland and attended Reed) where Snyder had arranged for some readings. Only recently did some folks at Reed find a box with a reel-to-reel tape marked "Snyder Ginsberg 1956," played it and heard a decent-quality 35-minute recording.
The date of the reading, at a student hostel called "the Anna Mann Cottage," is February 14 - Valentine's Day 52 years ago.
Here's an article about the find.