Has there ever been a year that started with as many changes at the very tops of the major music companies? The seeds for the current fluidity were sown when Lucian Grainge replaced Doug Morris as UMG’s Chairman/CEO in early 2011 and bought EMI the following year, transforming both companies. Gone were Morris, L.A. Reid, Sylvia Rhone and David Renzer, as well as almost the entire EMI team; Mike Dungan, whom Grainge had hired to run UMG Nashville prior to the acquisition, remained. Jimmy Iovine, of course, transitioned to Apple a few years later in one of the fattest deals ever.

In came—or became empowered—Steve Barnett, John Janick, Monte Lipman, Michele Anthony, Steve Bartels, David Massey, Big Machine’s Scott Borchetta, Cash Money’s Slim and Baby, David Foster, Jody Gerson, Will Tanous, Boyd Muir, Jeff Harleston, Jay-Z and Roc Nation and Scooter Braun, as Grainge created the behemoth that looms over today’s music-business landscape.

The coming year will see another tweak to the UMG colossus with the appointment of Paul Rosenberg as Def Jam head; Rosenberg has moved swiftly in appointing Steven Victor EVP/Head of A&R and, just this week, Rich Isaacson, who played a key role in the success of Steve Rifkind’s Loud Records, as EVP/GM. The new lineup affirms Def Jam’s mandate to re-establish itself as the preeminent hip-hop label, in keeping with its storied brand. The difference now, of course, is that every label has to be in the hip-hop business to compete. How will the advent of Rosenberg and his lieutenants affect the rest of the Def Jam team?

The most widespread transformation of the new year is underway at Sony Music, which is undergoing its second major change in a decade. Morris, Reid and Tom Corson are no longer part of the company’s management team, while Rob Stringer, Morris’ successor as Sony’s CEO of recorded music, has brought in SONGS’ Ron Perry to replace him as CEO of Columbia Records. (And following the SONGS sale to Kobalt for a reported $160m, Perry’s former partner Matt Pincus is scoping out high-end real estate on Nicaragua’s top surfing beaches.) Peter Edge loses a strong COO in Corson, but RCA appears to be hotter than ever, with the recently dropped G-Eazy and a pending set from the mighty Justin Timberlake further stoking the fire. Wonderers are wondering which member of RCA’s hierarchy will step up to shoulder the load alongside Edge, with names like Riccitelli, Fleckenstein and Naftaly naturally prominent on chatterers’ lips. At Epic, Rhone has a hot hand, seamlessly filling the void left by Reid’s departure and extending the label’s torrid six-month hot streak. Epic will soon be further strengthened with this week’s arrival of respected promotion/marketing exec Rick Sackheim from Def Jam as EVP.

Will the new teams be able to compete at the same high level they have over the last six or seven years, as the streaming model becomes the foundation for the fundamental economics of the business? Thus far, it looks like RCA and Epic have found that sweet spot, while industry eyes will be locked on the new Columbia, the big question being whether Perry will be able to recapture the zeitgeist and reinvigorate the label following a soft, off-cycle year. Big Red has been known for its cool superstar releases for the entire modern era, but streaming is changing the business into a more song-driven new-artist business. Signing some artists to address that situation is certainly job one for the incoming chief. How will Perry balance Columbia’s rich legacy and today’s morphing realities? The much-discussed Perry-Joel Klaiman partnership is said to be off to a greater start, with word from inside the company that the early vibe between the two is strong.

In terms of intriguing subplots involving familiar faces, how will the re-entry of Barry Weiss affect the new Sony architecture? People find his role interesting, given Weiss’ prior history at the company. The seasoned exec, who worked with several current Sony players back in his BMG days, will continue to oversee RECORDS, the imprint formerly affiliated with SONGS.

WMG, once the top music group, which had been decimated by poor management for more than two decades, has finally begun to turn the corner under Len Blavatnik and CEO Steve Cooper. Russian-born billionaire Blavatnik’s $3.3b investment in mid-2011—viewed by some at the time as a modest attempt to dip his toe in the entertainment waters—is now seen as a shrewd strategic move, as the value of the company has more than doubled over the last six and a half years. He and Cooper have anointed WMG U.K. chief Max Lousada to head of WMG’s recorded-music operations, and Lousada has chosen Corson and Interscope’s Aaron Bay-Schuck to rejuvenate Warner Bros. Records, which hasn’t broken a major act in more than a decade, while his U.K. company and his other U.S. label, Atlantic, have been over-performing. With Corson in the office and Bay-Schuck allegedly taking his new post in the fall, wonderers wonder: What’s the plan? Who’s in? Who’s out?

The publishing landscape is also occasioning much speculation, as Marty Bandier’s Sony/ATV makes its play to acquire a majority stake in EMI, the pubco gem he built and burnished for years. With an estimated price tag of $4.5 billion—and the expectation of multiple suitors in the derby—the EMI sale has underscored the issue of ever-escalating valuation in the pub world, alongside the big SONGS sale and other pricey catalog and company acquisitions. Investors clearly see copyright oversight as a keener investment than ever in the streaming era. Meanwhile, Bandier’s former protégés and current competitors, Jody Gerson and Jon Platt, are both highly coveted execs, coming off great years. Warner/Chappell boss Platt, recently tapped as a WMG board member, is enjoying terrific success worldwide. Gerson, having re-upped with a big new deal, has revitalized UMPG; in terms of marketshare, streaming and Grammy love, both are on fire.

Against this backdrop of change, several other interrelated themes will be in play during 2018: How big will Spotify become? With its SEC papers reportedly filed, will its IPO deliver on its fat promise? Speaking of filing, how will the new lawsuit from publisher Wixen alter the situation, if at all? Spotify has been in a tug-of-war with Apple Music over the weighting of streams on the industry bible’s chart, and is more than a little unhappy about the proposed new ratios, which diminish the chart value of ad-supported streams. Apple Music boss Iovine—whose platform has no free tier—has led the charge for such a change. Still undecided: Whether YouTube’s streams will be counted on the Top 200, a sore point for many who believe Lyor Cohen continues to hijack the algorithm.

Apple has seen significant growth over the last year, with total streams up 72% over 2016 totals, though it still lags behind the Swedish giant (which itself grew 37% in the same timespan). When Iovine steps down in August, who will become the new face of Apple Music? Will Cupertino’s streaming division coexist more or less happily with the biz in its next era?