What if Decca signed the Beatles?
Syd Barret never left Pink Floyd?
Otis Redding never died?
Or Stevie Ray Vaughn?
When I attended the Univ. of Wisconsin, the apartment building I lived in, was next to the lake (Lake Monona), that Otis Redding's plane went down in.
I've also been to concerts at Alpine Valley (where SRV died), and considering that the ski hill the helicopter SRV was flying in hit, is basically right behind the stage, it's not at all implausible that during bad flying weather, a pilot unfamilar with the area, could crash into the ski hill. It's too bad, because, Syevie had gotten himself cleaned up drug-wise (when I saw him headline at Summerfest in Milwaukee in 1986, he was so stoned, and his speech was so slurred, you could hardly understand him at times), and had recently released his "In Step" album, to reve reviews.
Regarding Syd Barrett - he did not technically leave/quit Pink Floyd. According to some interviews of David Gilmour I've read (he had had known the guys [including Syd] in Pink Floyd for a very long time, and when Syd [whose real name was Rodger] started getting erratic, and couldn't be counted on to pull his weight musically in the band, David was asked to join the band as the second guitar player), when the band was leaving for a show they were doing in Great Britain, somebody said, "hey, what about Syd?" The response given by another band member was basically that Syd was such bother to bring to gigs (there had already been some shows, where Syd was so out of it, that he did nothing but stare off into space, and strum the same chord on his guitar non-stop, irregardless of what was going on at the time), that the band should just head out to the gig, and not bother stopping off at Syd's place to pick him up (for the gig). That was that, and from that day forward, Syd was no longer included in Pink Floyd's musical activities. Also, David Gilmour has stated that while Syd's heavy LSD usage was a contributor to the breakdown of his mental state, it was not the only factor in it occurring - both David (and Roger Waters) remembered at least one time, where Syd had to be hospitalized when he was young, due to a nervous breakdown. LSD was probably the straw that broke Syd's mental back.
Two musical What Ifs of mine:
1. What if Cliff Burton, Metallica's gifted bass player (listen to the killer bass solo "(Anesthesia) - Pulling Teeth", off of the Kill 'em All album) hadn't died in the bus crash that occurred during their 1986 European Tour? IMO there was a definite shift in Metallica's sound after Cliff died.
2. This is sort of a two for one - how would have things went for Fleetwood Mac, if Peter Green (who was a major musical contributor to the band, and at the time was considered a guitar god), and Danny Kirwan (the band's third guitar player at the time - he was a very gifted player, who IMO, had a postive impact on Fleetwood Mac's sound) hadn't been enticed by the "German Jet Set" couple (bass player John McVie's name for them), to attend a party, where both Peter and Danny basically spent the next day or two fried out on LSD?
Neither of them really recovered from the experience. Peter Green ended up becoming schizophrenic, and as a result, spent a long period of time (at least 10 years) in a mental hospital, and while he's is back playing music sporadically, he's not the same as he used to be IMO, ability-wise. Danny Kirwan - nobody knows where he is. His mental state deteriorated, after the big LSD blowout, and he ended up leaving Fleetwood Mac. The most recent information about him (from a few years ago) is that he was living on the streets of London, as a delusional bum.
Without the event mentioned above occurring, would Fleetwood Mac have remained the blues, and hard blues-rock band it was at the time (despite the fact that before the LSD event, Peter Green was already contemplating leaving the group), or would it have eventually drifted into the more pop oriented direction that eventually resulted in the group becoming international superstars?