The 50's might be a tad too broad a range in this case, the recording industry was growing, and driving changes (improvements) in technology at a rapid pace.
Ribbon microphones did rule the roost, at least in the USA.
Stereo recording came about somewhere in the mid 1950s, prior to that it was all mono, and some studios would mix several microphones together to create that mono track - but mixers were pretty rare too.
The studios and control rooms were pretty crude by today's standards as well, well, that's not entirely fair, some of the sound stages of that era were really quite remarkable, but the smaller studios were not.
With all of that seemingly working against them they still made great recordings!!
Many of the recordings from the first half of the decade were made with a single ribbon microphone direct to disc, which in this case was wax master<G>. As the decade wore on they did start using more microphones, and they did start to record to stereo (actually left, center, and right).
You might want to do some surfing for information about Harry Olson, Bing Crosby and Les Paul, all of whom had quite a bit to do with early advances in recording, and happened to be smart enough to capture some of that history.