For many radio people, it was baffling. How did a radio station format change stunt that hearkens back to the beginnings of top 40 become a social media sensation, then spread even further? At a time when radio is rarely a consumer press story, or at least a positive one, the transition of Univision's "Latino Mix 105.7" to #Nelly105.7 showed up everywhere from Mother Jones to New York City's local TV news.

So after the endless loop of "Hot In Herre" stopped, what did the Bay Area's new Hot 105.7/100.7 do for an encore? It played some late '80s audio of the fondly remembered KHQT (Hot 97.7), the San Jose rhythmic outlet that was still a viable station when it was sold and changed formats. Then it played "Hot In Herre" one more time. Then, new p.m. driver Chuy Gomez, former morning host on KMEL, played "Baby I'm Back" by Baby Bash. 

And with that, #Nelly105.7 was now "The Bay Area's new No. 1 for the most hip-hop and R&B." 

It's a significant move in a few ways. For the last decade, Latino Mix and predecessor La Kalle 105.7, had been doing some form of younger Hispanic-targeted programming keyed to the mid-'00s reggaeton boom, then the rise of bachata. Reggaeton had, for the first time, helped bring Latinos under age 35 to Spanish-language music on a station that was at least bilingual. Now, for some broadcasters, the thinking is again that the best way to reach young Hispanics is with English-language music.

Hot 105.7 is also "hip-hop and R&B" at a time when many other rhythmic top 40 stations have reimaged themselves as "hits and hip-hop." After the top 20, the rhythmic chart becomes a mish-mash of dance and pop crossovers, along with the R&B and hip-hop hits. KYLD (Wild 94.9), San Francisco's longtime rhythmic outlet, has evolved to mainstream top 40, playing OneRepublic and Bastille. But in its first few days, Hot wasn't playing anything more pop-leaning than Lorde's "Team" and Pitbull's "Timber." 

Hot 105.7's change comes a few days after a less heralded but not insignificant return to rhythmic top 40 at KHHM (Hot 103.5) Sacramento, Calif.  A few years ago, both that station and rival KSFM had acknowledged the success of rival KDND (The End) by evolving towards mainstream top 40. KSFM backed off quickly, but for a moment, Sacramento -- a market where only rhythmic top 40 was once thought to work -- had no true R&B and hip-hop station. 

Up and down the west coast, the state of rhythmic top 40 varies by market. KUBE Seattle has gone more rhythmic, following the launch of gold-based rhythmic rival KHTP (Hot 103.7). KXJM (Jam'n 107.5) Portland has just modified its format and become more like Hot 103.7. Longtime hip-hop outlet KPWR (Power 106) Los Angeles has flourished recently, even with top 40 KAMP (Amp 97.1) on its flank. But XHTZ (Z90) San Diego plays One Direction and A Great Big World, meaning that there is no dedicated hip-hop and R&B station in that market.

None of those markets have a straight-ahead Hip-Hop/R&B station. In San Francisco, Hot is up against R&B/hip-hop KMEL (identifying itself yesterday as "the Bay's No. 1 for Hip-Hop and R&B"). Not many rhythmic outlets have found room recently by picking off Hispanic listeners in a market that already has a viable urban outlet, but the new Hot does have the advantage of Wild's evolution. It also has the potential to be San Jose's rhythmic outlet (the simulcast duo gives the South Bay frequency first), and the legacy of a once-beloved station that quit while it was ahead.

Here's Hot 105.7 on its third day, March 19, at 4:15 p.m.

Pitbull f/Ke$ha, "Timber"

Ty Dolla $ign f/B.O.B., "Paranoid"

Jay Z, "Tom Ford"

Chris Brown, "Loyal"

J. Cole f/TLC, "Crooked Smile"

Pharrell, "Happy"

Kid Ink f/Chris Brown, "Show Me"

Aloe Blacc, "The Man"

Jay Z f/Justin Timberlake, "Holy Grail"

Sage The Gemini, "Red Nose"

Rihanna, "Pour It Up"

Jhene Aiko, "The Worst"

Snoop Doggy Dogg, "Gin And Juice"