This was common in those days and I believe it has to do with noise handling on a very loud stage. Seen pics of Zep, Otis Redding, lots of singers using the dual vocal mic setup live in the 60s and 70s. Something to do with having the two mics feeding the same input, but the polarity of one is flipped to create almost like a humbucking situation to reject stage noise. Somebody school me in case I'm fucking that up. I know this was covered in the tech room in the old forum but I'm not sure if it survived. Can't find it. I was actually going to bring this up again in the tech room in response to Owen's guitar bleed problem.
Re: Favorite Sabbath record
41Radio show https://www.wmse.org/program/the-tom-wa ... xperience/
My band https://redstuff.bandcamp.com/
Solo project https://tomwanderer.bandcamp.com/
My band https://redstuff.bandcamp.com/
Solo project https://tomwanderer.bandcamp.com/