I lived in the NYC area in the 70s. I remember a station that changed format to progressive rock and took the call letters WQIV (as in Q for quad and IV, Roman numeral for 4. They went after the other progressive rock station, WNEW which had been doing that format for years. But "quad" was better, right?
They never told you what kind of quad it was. It was more a marketing thing than actually broadcasting in quadraphonic.
Just like when CDs came out. A radio station I worked for used "now playing all CDs" as one of our liners....but the CDs were from some company called Century. They were just made from tapes. Some of the songs had so much hiss on them! It was all about the marketing.
Edit: I stand corrected. I guess WQIV broadcast in QS. I found, on-line, the format change audio and they mention QS. I had never heard that back when I was listening on a regular basis. You can hear the change at about the 9 minute mark.
https://formatchange.com/104-3-wncn-new-york-becomes-rock-wqiv/