I've noticed a small uptick in AM music here. WABC 770 NYC was THE music station in 60's and 70's (frequently would announce their call letters as W-A-Beatle-C) and can be heard throughout the eastern half of the US. They switched to an all talk format in the early 80's. After a recent single owner, non-network purchase they have gone to full music on Saturday and Sunday evenings. Iconic WABC DJ Cousin Brucie from the music era and Tony Orlando (yes, THAT Tony Orlando) host on Saturdays, Joe Piscopo (formerly SNL) is behind the mic with Sinatra music on Sundays.
Local station WNTY 990 am Southington, CT now has an oldies music format which began during the past year. Finally, the former WQUN (eventual WATX) Hamden, CT is expected to return to the airways this summer with a music format. The explanation for a programming direction toward music by an AM station might be as simple as the old advice "Zig when everyone else Zags".