Interesting thread Kat. I believe it would have been in the early sixties when I first heard any sexually-alternative songs. Names that come to mind would be Chris Williamson, and Alix Dobkin. Of course Bessie Smith (who from all accounts, loved a good time,) probably put disguised references into her blues songs.
As far as Gay songs by guys, my guess is they would have been totally underground til at least the seventies. Fred Small was quite open and probably paved the way for others, but wasn't his debut in the mid-seventies at the earliest?
One of my favourite songwriters Paul Seibel ("Louise") didn't come out publicly til long after his great album "Woodsmoke and Oranges".
If I had to take a guess, I'd say that there were probably a number of small private (for safety sake) record labels that did exclusively Gay material from a way back. There is a long history of "in house" recordings. The Communist Party had it's own labels from the thirties. I've got an old "Charter" 78rpm from the forties with the as-yet un-named "Weavers" singing "Wasn't That a Time". I'm told that it was sponsored by the CP. Also I believe the KKK had their own label that recorded groups like the "Reinhart Bros". Of course there have always been small labels doing "comedy" records,(and I ain't talkin' Bob Newhart, folks). In the twenties (and probably before) there were very "Blue" recordings, that folks brought out at cocktail parties. My friend's parents kept a trove of these and he and I as 10 year olds used to find and play them. People like B.S. Pully, and even Sophie Tucker. We didn't understand them of course, but we "knew they were wicked"!
So my guess is that were probably gay records and artists from the early days, but you had to be "in the know" to find them.
Correct me if I'm wrong someone, but weren't Peter Pears and Benjamin Britton (sp) openly gay a long time ago?