C-Man I think I got it!
First I went through the entire products page on Wikipedia and googled images of all the ones that were around in '85. There was only one that was a close match:
http://www.sinkardd.com/img/9c0/f99/9c0f994b642c75d21f25b12f7467e6aa_0.jpgIt didn't have the short keyboard, but that could be an optical illusion. Also, it appears to have an edge that falls away whereas Brian's keyboard, the right edge seems to be flush to the keys. But the design is about the same...keyboard that ends at G, the grooves on top without a program bay, the color, etc. It does not appear to be THE keyboard. But it's close. What makes it more confusing is even THIS keyboard - the PF-50 - seems to be a Japanese model and different in design from all the other ones I can find on the 'net.
Now, at 6:36 there's a shot of Bruce's keyboard which looks like it may be the same model. On this one you can see the groove area on the right hand side of the keyboard, and what may be the green program bay similar to the DX's just to the left of it (below the scrap of paper) and a bunch of buttons at the far left. The rest of the top of the keyboard seems to be smooth. The keyboard however appears to be different; definitely a full size and it looks like the top key is a (more typical) C.
So I tried another tack: I figured Yamaha would probably have donated new models to LiveAid, so I googled for the 1985 catalog for their keyboard line and lo and behold, it was online! And my hunch was right, they were all keyboards in the new product line for '85, and not the models I saw on the net.
Here's the link, with the picture at right:
http://brochures.yokochou.com/keyboard-and-effector/yamaha/1985/en_p23-24.htmlBrian's playing a PF-12. Shorter scale keys, top key G. Bruce is most likely playing a PF-10; on closer examination there's a split second where the camera is close to the keyboard and from that angle it does look like this is a keyboard that tops out at G and not C, and since the PF-10 appears to have longer scale keys than the other two, I think that's the one.