The Music People jingle package has been discussed here before and you have the story pretty close to the way Jeff described to it, Chas. As I heard the story (direct from The Man), the "Now Radio" package outlasted its shelf life. Armstrong mocked it on the air ("...look at 'em, walkin' out in droves...") IMHO, "Now Radio" was hokey. But I can understand how and why some people liked it.
The era, the music being released, the groups, and the competition in the market demanded a stronger package. Jack was used to more powerful, albeit off-the-rack jingles in Denver (KTLK) and Toronto (CHUM). Jeff wanted a jingle sound that set WKBW apart from anything heard on radio and Top 40 radio in particular, matching the KB personalities like Armstrong, Beach, Berns and Neaverth. Format competitor 1400 WYSL was using a very good package, similar to what was heard on CKLW. WYSL's package offered more jingles, transitions, slow to fast, fast to slow; shotgun types, full up, medium as well as smooth down tempo, with full orchestration and acapella. Those were very good jingles, but Jeff didn't want stock jingles. Nor did he want a "Seventy Seven W-A-B-C" sound.
It was all about differentiation. So on some cuts, the session singers were replaced by a bar band singer that they'd "discovered." These are the cuts that sound like David Clayton Thomas, Crow, Jethro Tull, Zepplin, Mungo Jerry and Chicago. If you listen closely, the bar band male singer sings "dubba you" on some cuts, "double you" on others. But there are session singers in The Music People package, and they're very good, heard especially on the smooth cuts that are styled after Joni Mitchell, Bread or Carole King, as well as some uptempo tracks like the Badfinger sound-alike. These, BTW, are altogether different from the Pop-Tops that came a bit later.
There were so many cuts and mix-outs on The Music People package, that it still amazes me when I hear them on airchecks. Armstrong's patented "Your leeeeader" howl is best remembered as it's done over the jingle featuring a Chicago-like arrangement. It's a ramp-up jingle that leads into the sing: "WKBW... The Music People." And Berns' use of jingles to close out bits or shtick was equally classic.