It’s been a long while since I last posted here on the subject of microphones and the bluegrass music. The sound amplification scene has changed drastically since the 1950s, when I first encountered mics. In Chicago in 1961, I met a cosmic ray physicist at the University of Chicago, who invited me to his home in Evanston, where he and his wife recorded a few folk songs with an EV ribbon mic. 
These were great for recording, but too fragile to use as PA mics. Dynamic mics, a little tougher than the ribbons, had begun to be used. I recall playing the Ash Grove in Hollywood, whose stage had been set up by a fine audio engineer, complete with EV-666 dynamic microphones. PA mics in those days had a more relaxed, wider pickup pattern than modern mics, tailored to use by rock musicians, who most often sing (or scream) into the mics at 1/2 inch range. These misc necessarily have an extremely tight pickup pattern to avoid feedback from the stacks of instrument amps usually right behind the singers.
First generation bluegrass bands generally had one single mic at hand, and placed themselves around it to regulate their sound — as mentioned in a previous post. That would be impossible with modern PA mics, which are now stretched out across the stage in a single line, often two to a musician (one for vocals, one for instrumentals.) Us older folks miss the ballet-like gymnastics of earlier band members as they traded places around the single mic setup. It added a certain dynamic to the performance.
Bobby Hicks and Gorden Terry twin up a fiddle tune for Bill Monroe, around a single PA mic. Those were the days!
Friends now convert their acoustic instruments with electronic pickups (piezo transducers) and built-in microphones. The most advanced use a blend of the two devices to feed a signal to the sound board. They claim that the sound is just as good or better than facing a mic on a stand, but my experience has been that it is instantly possible to hear the difference between a built-in device to a stand alone mic. I can hear the crinkling sound of transistors that instantly gives the device away. To be played properly, bluegrass requires that a microphone be used.
Recently, I was lucky enough to be loaned a pair of Sony C-37A mics from the early 1960s. They are tube condenser microphones, with special, custom-built power supplies, and their sound is truly magnificent.
Twin pair of Sony tube condenser mics, as used to record a stereo sound image.
I’m having a wonderful time, trying out songs, tunes, and instruments in front of them. Because of the configuration, I am recording a true, stereophonic sound image — something one rarely hears in these days of multi-layered “tracks”.
Here’s the special power supply, built by my friend, using the original Sony transformers. Man, what a great sound they create!
Custom built power supply
As one sound experiment, I tried recording an old version of the folk song, “Billy The Kid”, using this mic setup. This was just a trial run, single take, but I hope some small part of the microphone’s sound comes through the linked video . . .
