During the instrumental introduction to “Lucy in the Sky With Diamonds” (Elton John’s version) , what instrument is that? …Sounds like a synthesized harpsichord? 
It’s a guitar played through a Leslie (a rotating organ speaker) in unison with piano.
The inside of a Leslie speaker.
And a bit about the Leslie speaker itself.
And a nifty video with great Leslie audio samples.
I’ve only seen one Leslie up close. True to form, the cabinet was utterly beat to shit when we walked up to it. It was backstage near the loading dock at the Thunder Bay Community Auditorium in Thunder Bay, Ontario. It looked like hell but sounded like heaven.
The guitarist in the band I was touring with went insane, plugged in and was just so very very happy.
You think it might have been Paul Schaffer’s, once?
[quote=“Jinx, post:1, topic:770288”]
Sounds like a synthesized harpsichord? /QUOTE]
You can’t synthesize a harpsichord, the plectra wouldn’t like it.
Dennis
Crazy! I’ll have to look into this further. But…what other pop song used this device? Or, did it just sit on the shelf pretty much like Frampton’s voice thingamambob?
Is anything really rotating? From the links to pics inside a Leslie speaker, I expected to see something that rotates to distort the sound. But, I don’t see anything surprising, really (unless I am mis-seeing what I think I am seeing)?
Wikipedia says the two speakers themselves are what rotate. One is treble, one is bass.
Looking at Cartooniverse’s link to the inside of a Leslie speaker, the woofer (speaker) on the bottom is ported through a baffle that is rotated by a motor and belt. The horn driver (the gold-brown thing above the woofer in the same cabinet bay) sends sound through a couple of black horns that are rotated by a second motor. Fig 1 in this link also shows the layout.
If you look at the picture next to the Wikipedia article, you’ll see that the speaker (right side, facing down) is solidly mounted. Beneath it is the rotating assembly that spews the sound around. You can’t see the scoop bit of the rotating assembly, but that is what directs the sound from down to out. You can also see the high frequency driver, just above the speaker, which is likewise bolted in. The rotating bit for HF is the black plastic double-horn thingie above same.
Wikipedia is incorrect when it says “modifying the sound by rotating the loudspeakers”–they don’t rotate.
Or as I like to say “that turns out not to be the case.”
Here’s a video of the inside of a Leslie in action. At about 30 seconds in, the organist switches from the slow (“chorale”) to fast (“tremolo”) mode.
So, I am confused. This is an organ run through a Leslie to enhance the organ sound? Still sounds like an organ, perhaps more pipe organ-ish than simply electronic keyboard. Was thsi a common technique of the 60s-early 70s? Apparently, “Green Onions” is also run through a Leslie; yet, an organ still sounds like an organ.
Searching Youtube for guitar w/Leslie, I gotta admit the guitar sound run through a Leslie is incredibly surprising - for acoustic and electric guitar! Now, I gotta re-listen to my rock collection and “look” for instances of the Leslie speaker sound! This is so…whoa! Cool! 
There’s a warble and thickness in the sound that the Leslie makes. It’s probably a bit more noticeable on guitar than organ, but to me the guitar still sounds like a guitar with a chorus-type effect on it. And it’s also possible that part of what you are calling the organ sound is that because the Leslie is pretty much associated synonymously with the Hammond tonewheel organ sound.
OK, one more question about the Leslie and “lag”. Here is a Youtube video of someone playing “Green Onions” on an keyboard run through a Leslie - engaged at certain times. How come one does not detect a lag in the sound as the Leslie comes up speed? I mean, I would expect to hear something like the drawn-out sound made by a siren ramping up to full wail? For example, notice the Leslie starting up at about the 2:20 mark coming to full speed at about 2:28. At least, I don’t detect any lag as the Leslie spins to full rpms…do you?
There’s not much lag, but there’s a definite difference in tone as it slowly kicks in at 2:20 and then is switched on to full tremolo at 2:28. The ramp-up sounds noticeable to me once it gets to 2:28 until it hits full speed at about 2:30 or 2:31 or so.