Not that I was there… but if you look at amp development and string development throughout the 1970’s you can see that most of the influential bassists were playing roto 66 rounds, as the trend was to make your bass guitar as trebly as possible. I’ve also spent a lot of time simply talking to people who were there. Yeah flats were popular especially to a lot of country guys but every single one of them mentioned rotosound rounds as being very prominent back then.Roundwounds didn't really become popular until the '80s. The '70s were still mostly (not exclusively) flats.
But again… I wasn’t there…
