This isn't what Jennifer Lopez wants to hear as she comes down from the high of the two-hour season finale of American Idol (and as she weighs the decision of whether to re-sign for a third season with the hit show), but her current single seems to be running out of gas on the Hot 100. "Dance Again," featuring Pitbull, drops from #17 to #19 in its seventh week. Singles often move up and down, but since J.Lo's twice-weekly Idol visibility is coming to an end, at least for this season, it's starting to look like #17 will be this record's peak.

By contrast, "On The Floor," J.Lo's 2011 collaboration with Pitbull, logged 15 weeks in the top 10, peaking at #3. I don't think "Dance Again" is as striking as "On The Floor." As Randy Jackson might say, "This one was just OK for me."

Adam Lambert's Trespassing enters The Billboard 200 at #1, displacing Carrie Underwood's Blown Away. This marks the first time that artists who rose to fame on American Idol have had back-to-back #1 albums. Lambert was the runner-up on Season 8. Underwood was the winner on Season 4.

Lambert is the second Idol runner-up to land a #1 album, following Clay Aiken. One other Idol "loser" has topped the chart: Chris Daughtry, who finished fourth in Season 4.

Photo by Frank Hoensch/Getty ImagesRobin Gibb died in a London hospital today after a battle with colon and liver cancer. He was 62. Robin's series of health crises began in August 2010 when he underwent emergency surgery to treat a blocked intestine. The same hereditary condition led to Robin's twin brother Maurice Gibb's death in January 2003 at age 53.

Gibb's family released a statement today, saying: "The family of Robin Gibb, of the Bee Gees, announce with great sadness that Robin passed away today following his long battle with cancer and intestinal surgery. The family have asked that their privacy is respected at this very difficult time."

[Related: 2012 Billboard Music Awards Photo Gallery]

Gibb's death puts a spotlight on Bee Gees, one of the most successful groups in pop music history. The brother trio, which also included oldest brother Barry Gibb and Robin's twin Maurice, amassed nine #1 hits on Billboard's Hot 100, a total matched by only two other groups or duos. The Beatles lead with 20. The Supremes had 12.

I'm sure that Jimmy Iovine tried to be fair and even-handed in selecting songs for the top three contestants on American Idol, but his choice for Joshua Ledet, the Mary J. Blige hit "No More Drama," put Ledet at a disadvantage. It's not that "No More Drama" isn't a great song. It's that it's not as well-known to a broad TV audience as the songs that Iovine chose for the other two contestants.

"I'll Be There," which Iovine selected for Jessica Sanchez, has been a #1 hit twice, for the Jackson 5 in 1970 and Mariah Carey in 1992. "We've Got Tonite," which he chose for Phillip Phillips, has been a top 15 hit twice, for Bob Seger & the Silver Bullet Band in 1979 (#13) and for Kenny Rogers & Sheena Easton in 1983 (#6). (That duet recording was also a #1 country hit.) By contrast, "No More Drama" has been a hit just once, for Blige in 2002. (It reached #15.) "No More Drama" is a signature song for Blige, but these other songs, by virtue of the covers they've received, are contemporary standards. If there was a modern-day "Great American Songbook," they'd be in it.

Donna Summer was universally hailed as "the Queen of Disco," but the title didn't really do her justice. Summer had a big, powerful voice that would have served her well in any era. Such Summer hits as "Heaven Knows" and "On The Radio" were really just great pop records with a dance beat. But because of her strong association with disco, when the disco bubble burst in the early 1980s, Summer's career also suffered.

But while she was hot, she was on fire. Summer had eight consecutive top 10 hits, from "Last Dance" in July 1978 to "On The Radio" in February 1980. All eight were certified gold by the Recording Industry Assn. of America. "Last Dance," which Summer sang in the 1978 movie Thank God It's Friday, won an Oscar as Best Song.

Train's "Drive By" inches up from #11 to #10 in its 18th week on the Hot 100. It's the slowest-rising top 10 hit since Lupe Fiasco's "The Show Must Go On" cracked the top 10 in its 21st week in May 2011. This is Train's third top 10 hit. All three songs have taken their sweet time to get there. "Drops Of Jupiter (Tell Me)" took 14 weeks to crack the top 10 in June 2001. "Hey, Soul Sister" took 16 weeks to break through in January 2010. "Drops Of Jupiter" wound up peaking at #5. "Hey, Soul Sister" reached #3. Both songs won Grammys. "Drops Of Jupiter" was voted Best Rock Song of 2001. "Hey, Soul Sister" won for Best Pop Performance by a Duo or Group with Vocal for 2010.

Adele's 21 this week becomes the 24th studio album to sell 9 million copies since 1991, when Nielsen SoundScan began tracking sales for Billboard. Studio follow-ups to the first 23 have achieved varying degrees of success. On the high end, Backstreet Boys' 1999 album Millennium has sold 120% as many copies as its predecessor, Backstreet Boys. On the low end, Usher's 2008 album Here I Stand has sold just 13% as many copies as its predecessor, Confessions.

I took a look at the studio follow-ups to the 23 studio albums that have sold 9 million or more copies since 1991. I focused on how well they sold relative to the sales of their predecessors. I then assigned each a letter grade.

Adele's 21 tops the 9 million mark in U.S. sales this week. It's the first album to hit the 9 million plateau since Usher's Confessions hit the mark the week ending July 24, 2005. Remarkably, 21 reached the 9 million plateau faster than Confessions did, even though overall sales were much more brisk in 2004-2005. 21 has been out for 64 weeks. Confessions took 70 weeks to reach the magic number.

21 is the 29th album to sell 9 million copies since 1991, when Nielsen SoundScan began tracking sales for Billboard. It's the 24th regular studio album to reach this level. Studio follow-ups to the first 23 have achieved varying degrees of success.