By Sean Ross of @RossOnRadio

Neither Justin Bieber nor Adele left mainstream top 40 radio on bad terms. But both were gone for a while.

Throughout 2012, Bieber gave top 40 the grown-up rhythmic pop they’d been waiting for and found a receptive home for the singles from “Believe.” Only the last one, “All Around the Word” didn’t become a sustained hit. The stray songs that trickled out during Bieber’s personal travails of the next few years never went to radio and did nothing to lower the singer’s batting average at the format.

After the hit singles from “21” ran their course, Adele might have tested top 40’s goodwill just a little in 2012 with the funereal James Bond theme, “Skyfall.” The stately “Somebody Like You” had proved that ballads weren’t really PPM poison, and paved the way for other equally pensive piano pieces. But there were limits and “Skyfall” generated just enough fallout to ensure that Adele’s eventual return with a new project would be an interesting one.

So do call them both a comeback anyway, because both artists have been gone for years. Bieber’s new “Sorry” (the second pre-release single from his upcoming album, “Purpose”) and Adele’s “Hello” (the leadoff track from “25”) came out within a few hours of each other on Thursday/Friday (October 22-23). In Nielsen BDS, “Sorry” edged out “Hello” at Mainstream Top 40, entering that chart at No. 30 vs Adele’s No. 36. In the Mediabase chart on AllAccess.com, Adele actually did better, entering at No. 30, one chart position ahead of Bieber.

Even an effective tie between Adele and Justin Bieber is rife with comic possibilities, but it’s easy to declare a win/win. “Hello” got the hourly iHeart Media CHR premiere slot on Friday and opened with as much love as a stately five minute ballad, from an artist who’s been away from the top 40 charts for three years, could have hoped for. Phenomenal early sales will buoy “Hello” in the weeks to come, and it will probably reach the CHR top 10 before we know how it researches (well, I’d expect).

And in many ways, top 40 is Justin’s world. He’s just returning to it, having defined the format even during his absence. It was that other Justin who proved that former teen idols could make the rare Michael Jackson-like transition to adult artistry, or at least become consistent adult hitmakers. But it was Bieber, not Timberlake, who paved the way for the incursion in recent years of medium-weight rhythmic pop from Selena Gomez, Nick Jonas, Demi Lovato, Miley Cyrus, One Direction, Shawn Mendes, Ariana Grande, Hailee Steinfeld, and maybe even Taylor Swift. Bieber also proved that acting out in public was by no means a stopper.

Bieber also managed a feat that not every artist could pull off: the soundalike follow-up. “What Do You Mean?” is its own record now, but tell me that on the Friday morning of its release, it didn’t sound exactly like “Where Are U Now” for a few moments, down to the title. Omi’s soundalike “Cheerleader” follow-up, “Hula Hoop” continues to struggle at CHR, but “What Do You Mean?” has already been in and out of No. 1, paving the way for “Hello.”

It’s the post-Bieber combination of the uptempo rhythmic pop-youthful artist formula that gets the nod most easily at mainstream top 40. X Ambassadors or Elle King’s pop/rock singles wait for months while Tori Kelly or Hailee Steinfeld are ushered in ahead of them. Those songs may not become powers, but top 40 is willing to accommodate them as “B” or “power new” for a few weeks until they know. It will be almost impossible for the forthcoming Arianna Grande to NOT enter the chart above No. 30 in its first week.

Adele’s influence on mainstream top 40 hasn’t been quite as obvious on a week-to-week basis, at least not since the Bruno Mars/Pink/Rihanna troika of piano ballads ruled the chart at once. But there’s always another record made possible by “Someone Like You” at some point, the best recent example being “Take Me To Church.” In fact, if you sum the placidity of “Someone Like You” and the techno-throb of Bieber’s “As Long As You Love Me,” you get a lot of what’s on the charts now—the Ellie Goulding chillout pop that alternates between gurgling and grinding.

One final note. Last Friday morning, I listened to the Adele song via e-blast, then punched around both New York radio and U.K. radio, hoping to find it on the radio again. Although we think of the reaction to “Hello” as having been phenomenal, it actually took an hour before I came across the song on New York’s WWFS (Fresh 102.7). The only other sighting was another morning show that was goofing on the Lionel Richie song “Hello.” I don’t think that’s because New York radio failed to acknowledge “Hello.” It’s just further proof that listeners’ exposure to what we do is never what broadcasters think it is.