It's played by Doctor William Scott Bruford, aka Bill Bruford, formerly of Earthworks, formerly of King Crimson, fomerly of Bruford Levin Upper Extremities, formerly of Anderson Bruford Wakeman and Howe, formerly of Bruford, formerly of UK, formerly of Genesis (touring only), formerly of Yes. And indeed this is a Yes song, a little-remembered ditty by them known as "Roundabout."
The fill in question occurs at 6:28 of the original recording, but here is it, semi-isolated for your listening pleasure. (I've chosen the version that's got Chris Squire's thunderous bass, and a little bit of Jon Anderson's vocals, for context, but there's also a version that's just Bill Bruford and, yes, entire days have gone by where I've just played his isolated tracks on repeat and so what if I do?)
The clip embedded should start seven measures before the fill, at 6:20. The fill itself lasts for one measure, so you can be prepared for the greatness, which begins at the 6:33 mark.
Here's what la partie de batterie inégalée sounds like without the bass (more or less):
There are at least two different transcriptions of this fill currently online. One looks like this:
while the other like this:
You'll note both agree on the first eight 16th notes, but then diverge as to what he does with the second half of the fill. While I find the first version more aesthetically appealing, the second version sound more correct to me, if still not quite accurate: I think it's correct in its number of bass drum notes, but I think Bruford used two different floor toms, where it only notates one. On the other hand, I've listened to the fill at half speed a dozen times and could never have even made a stab at notating this myself, so I'm probably wrong too and massive props to those devoted and erudite scholars.
Here's the thing that makes this fill so astonishing. First of all, it just is: it's technically difficult, it fits the music, it kicks the music into an even higher gear, and it sounds cool as fuck. But much or most or all of that could be said for so many other drum fills, so why this one? Because while technically difficult, it's far from the most difficult: there are oodles and boodles of fills by jazz and metal drummers which would make this seem rudimentary.
Two main reasons. The first is that it was improvised—unlike many other difficult fills which are planned, written, practiced ahead of time, this is jazz devotee Bill Bruford we're discussing, so this fill was, as with most of his fills, totally spur of the moment, played for that take and that take only, and never repeated. It just came to him as the measure approached, or maybe didn't even, maybe his limbs just took over and that's what happened.
The other thing is that this fill doesn't really sound like Bill Bruford, per se. I mean, it obviously does, and not just because he's playing it. But it's not as typical a fill as, say, the one he plays in the eighth measure of the song:
or the brief one shortly before the greatest ever:
I've always loved this other fill, incidentally. It's so short, it's almost like he refuses to do a typical rock fill, just tossing this unexpected bomb off casually, with the crash coming in on the 4 of the bar, rather than the 1 of the next measure, as is far more typical and would therefore be expected. As Bruford once said:
"Surprise, attack, understate, or overstate, but whatever you do, avoid the two cardinal sins of being either boring or predictable."("And when in doubt, roll.")
But the main fill, the fill we're talking about, doesn't really sound like him. It's not like when Ringo swings a fill, as was his style, even during songs with a straight feel. It's not like a Bonham triplet, which are always awesome. It's not like when Collins plays double-speed at the end of a fill, as he so often did. It's not like when Tony Thompson would end a fill with an accented snare on the 4 at the end of a fill, before crashing on the subsequent 1. It's not like Steve Gadd's fill that kicks "Chuck E.'s in Love" out of the bridge and back into the song, which is so badass and so tasty but quite stylistically typical of Gadd in every way (including being badass and tasty). Those are all awesome and part and parcel of those awesome drummers' awesome styles.
But this ain't that. This fill is atypical of Bruford, it's a one-off, which sounds like nothing he'd ever do again, even as timbrally it sounds so clearly Bruford. Put all those factors together and you've got the single greatest fill in rock history, on a song which has been played to death for 50 years, and yet somehow it still skates by unnoticed.
[For the record, the greatest drum intro ever is, of course, on the Temptations classic "Ain't Too Proud to Beg," played by one of the Funk Brothers drummers—in this case, apparently, Uriel Jones (and not the also amazing Pistol Allen or Benny Benjamin). Unbelievably versatile, musical, tasteful and kickass, it easily beats out, in my mind, also phenomenal intros by the likes of Charles Connor, Ringo Starr, John Bonham, Stevie Wonder, Steve Gadd, Stewart Copeland, Phil Collins, Jeff Porcaro, Larry Mullen Jr, Dave Grohl and so many other brilliant drummers.]