In April, Rob Stringer will become the sixth CEO of Sony Music during the last 45 years. Stringer follows in the big footsteps of Doug Morris, who took over from Germany’s bumbling Rolf Schmidt-Holtz in 2010. Schmidt-Holtz replaced Andy (rootkit) Lack, the wrong guy at the wrong time, in 2006. Lack succeeded one of the dominant record men of the 20th century, Tommy (Don) Mottola (1988-2003), who, if he hadn’t treated Sony Corp. Chairman Sir Howard Stringer so disrespectfully and incessantly watched Coppola and Scorsese movies, would still be there. Mottola wrested the job from Walter Yetnikoff (1975-90) when he self-destructed from substance abuse and an ego as big as Cleveland. Yetnikoff was driven out by David Geffen, Walter’s consigliere Allen Grubman, Jon Landau and Mottola, who was then Walter’s personally appointed number two, replacing Al Teller (1985-88).

Will the announcements of Stringer and Morris’ new roles create a domino effect in the music business on such a scale that it could impact Universal and Warner as well as Sony? Historically, when major changes like this happen, the answer is usually yes, as one key hiring can set off a chain reaction that results in moves being made for years to come in some cases. Consider, for example, how the exits of Steve Barnett from Columbia and Jimmy Iovine from Interscope changed the landscape, with strategic moves continuing to be made in the wake of those departures. There is an ongoing parallel domino effect in Britain, precipitated by Sony U.K. chief Jason Iley’s latest team-building move, naming Ferdy Unger-Hamilton President of Columbia’s U.K. unit. Insiders say there will be more to come in Blighty in the next few months.

Those close to Sony say that Stringer is in no hurry to hire his replacement as CEO of Columbia. Stringer’s deep relationships with acts on the current artist roster won’t end when his new role as CEO of Sony Music begins. The search for the right person to replace Stringer is expected to take some time, because he’s supposedly looking for someone with creative sensibilities similar to his own in terms of both A&R and marketing. Being able to sign top acts has always been the hallmark of the most successful label execs, and you can bet that Stringer will continue to flex his muscles in that arena.

Not surprisingly, most of the top candidates are currently under contract—but we could see a deal that would start at the end of that executive’s term, to be announced sometime before that term expires—a practice periodically employed by both Sony and Universal during the last decade. It’s said that the WMG group’s top execs are more vulnerable because of the nature of most of their employment contracts, with their shorter terms and lower compensation packages than those of their counterparts at Sony and UMG. This new label head will be responsible for building the future artist roster of Columbia, a job that ideally could last for five-to-seven years. Most consider the top post at Columbia the premiere label job in the entire business, and the short list of former occupants of the office is a who’s who of the modern record business: Barnett, Don Ienner, Teller, Bruce Lundvall, Clive Davis and Goddard Lieberson, to which we’ll add the name of legendary A&R exec John Hammond, the original architect of Columbia’s creative culture.

All the top execs at Sony’s current label teams in the U.S. are expected to stay in their current positions. Don’t look for a breakup of the Edge/Corson tandem at RCA or the Reid/Rhone team at Epic, in that those combinations have been consistently effective during the last few years. Reid’s move to Los Angeles gives Sony its first real West Coast presence since the disastrous Ayeroff-Harris WORK Records venture of the ’90s, following their successful run at Virgin, which ended when Branson sold the company to EMI and left the label in the hands of Ken & Nancy Berry, who toileted the company in short order.

Reid’s relocation to L.A. was being planned from the moment Iovine left Interscope for Apple, because Morris saw that Iovine’s exit would create an opening for a top creative exec to make a big impact on the West Coast. Unlike chief competitor Universal, which has maintained an East-West balance, Sony has never had an effective West Coast team. Warner had dominated the L.A. music scene until the mid-’90s, when the company self-destructed under the combined hands of Bob Morgado and Michael Fuchs following the 1992 death of Steve Ross.

At Columbia, it’s expected that Joel Klaiman will be given more responsibility in the running of the diskery; will a presidential title be headed his way? Meanwhile, Morris will continue to offer his unconditional support and sage advice to the team he assembled. He’ll begin his new multiyear chairmanship role feeling that he has put together a great winning team.

NAMES IN THE RUMOR MILL: Irving Azoff, Cliff & Peter, Guy O, Silva, Dickins, Griffiths, Tony D and Elliot Roberts.