Back catalog is often called the backbone of the record industry, and it showed plenty of spine in 2010. Michael Jackson was the top-selling artist last year, moving more than 8.2 million units in the wake of his unexpected death, according to Nielsen SoundScan. The Beatles came in third among bestsellers, behind Taylor Swift, shifting nearly 3.3 million of their re-released catalog — with no digital tracks available.

While these massive numbers indicate catalog’s clout, the major labels’ catalog divisions have had to radically shift their strategies as the landscape for physical releases has altered drastically in recent years. Deep-catalog retail chains like Tower and Virgin Megastores have disappeared, and the remaining retailers have diminished their floor space for music.

“Our release schedule has decreased significantly,” says Bill Gagnon, senior vp/general manager of catalog for EMI Music North America. “Titles that would have been carried at a Tower or even a Sam Goody, which are no longer in place, no longer have a home. So we’ve eliminated those off the schedule and chosen to focus on the big-event titles.”

EMI, which successfully reissued the Beatles catalog with a retail-based event last Sept. 9, hopes to duplicate some of that excitement with a John Lennon campaign in October that will launch the late musician’s remastered catalog, a themed four-CD box and a hits compilation into the market. Similarly, the company is reissuing 15 Apple Records titles that month.

“Now, in this day and age, you have to combine an event and significant promotional activity to drive the business,” Gagnon notes. “Otherwise the retailers won’t carry the product.”

Universal Music Enterprises, Universal Music Group’s catalog arm, created its own event in May with the re-release of the Rolling Stones’ 1972 opus “Exile On Main St.” in a plethora of configurations, from a single-disc version to a boxed set including both expanded CD and vinyl versions.

“We create packages that at each price point are of value to the consumer,” says UME president/chief executive officer Bruce Resnikoff. “That may mean single record, double record, deluxe edition, unreleased tracks, liner notes. I think the shrinking of the retail base has hurt people who think in the one-size-fits-all mode.”

And while the new “Exile” chart numbers (under 182,000 at last count) might not seem impressive compared to, say, those of Swift or Eminem, the hype surrounding its release helped raise the public’s awareness of the Stones catalog overall, generating the kind of dividends that can’t always be measured.

UME has backed away from selling most big-ticket boxed sets at retail, moving them instead through its Web-only Hip-O Select line. “We have to be realistic as to where the consumer is for any particular piece of product,” Resnikoff says. “With the shrinking traditional retail base, there’s clearly less of an opportunity to carry some of the higher-end and more intricate products that would have been carried by the record stores with 30,000 different titles.”

However, if lightning strikes and demand for a particular package grows, as it did with Verve’s four-disc Ella Fitzgerald set “Twelve Nights in Hollywood” last year, UME will take a Web-only set to retail.

Sony Music Entertainment’s Legacy Recordings enclave is attempting to offer something for every pocketbook with a spread of titles ranging from two-CD editions of classic albums to ultra-limited boxes sold through custom sites.

“The determination and the strategy to create the right musical offering,” Legacy senior vp/general manager Adam Block says, “the right musical experience for a fan at 99 cents or $9 or $90, really does reflect the fact that, in our view, the marketplace is fragmented.”

At the top end, that means products like the 30-CD “Complete Elvis Presley Masters” and the 43-CD “The Genius of Miles Davis,” limited to 1,000 copies and 1,955 copies respectively, and sold exclusively through dedicated Web sites. At the other end, that means titles like Ozzy Osbourne’s “Blizzard of Oz” and “Diary of a Madman,” which will be sold in both expanded editions and a deluxe, four-CD/DVD/two-LP boxed edition with a 100-page booklet. A new Jimi Hendrix anthology, “West Coast Seattle Boy,” is planned for October release in several editions of varying size.

“We are making many more individual types of product,” says Block.

At Warner Music Group’s Rhino Entertainment, where the modern boxed set business was fundamentally originated, most of the company’s high-ticket collections — like the recent four-disc Delaney and Bonnie/Eric Clapton live set — are now funneled through the company’s direct-to-consumer Web line, Rhino Handmade.

“If you look at what is required to make back the money you have to invest in some of these boxed sets, the perils of putting it out into the retail marketplace are greater and greater,” says Kevin Gore, Rhino president and CEO. “The more deluxe packages seem to have greater traction right now in the D2C channel.”

So, though Rhino will issue a four-CD Bee Gees retrospective via Reprise in November, the company is increasingly looking at more modest packages, like the recent three-CD edition of the Cure’s “Disintegration” and the forthcoming re-release of Pantera’s “Cowboys From Hell.”

Unsurprisingly, considering WMG’s ongoing preaching of the digital gospel, Rhino is also plotting an expanded digital course.

“Rhino’s legacy of creating compilations and packages, and, in the case of the digital side, playlists that allow people to consume our curated compilations is the place we’ll be focusing our efforts online, digitally versus physically,” Gore says. “In the digital space, your shelf space is unlimited. Then it’s just a matter of how you market and drive people towards those compilations.”