I measured 4 different passes of the riff on a grid at 141 bpm. Seemed to be the closest approximate tempo.
On the album, the riff was played loosely, and it wanders around the pulse, slowing down and speeding up by small amounts. None of the passes through the riff exactly line up. (So it wasn’t recorded to a click.)
They were probably just playing the riff together in the room and feeling it out intuitively. I doubt that when they played it, they were counting it out. It’s a short enough riff that an odd-meter player can get the hang of it pretty quickly.
(Since Bar McKinnon played sax on this, he would be a good person to ask.)
HERE WE GO:
There are 7 notes in the riff. They are D-C#-G#-C-B-F#-F
(Trevor seems to like writing in these chromatic groupings that are similar to 12-tone rows, but not using the full 12 notes. I’ve found several of these on the debut album as well.)
Counting in 8th notes, the notes would be these lengths:
You could divide that into two big measures:
14/8 and 13/18
Or you could think of it as one very long measure: 27/8 Time Signature
Or some other combination.
I would simplify it as this:
4/4, 3/4, 3/4, 7/8
That would be the most straight-ahead count, as I used in the notation above.
But, since the pulse is wandering, it’s possible Trevor intended the sequence to be this:
On some of the passes through the riff, the final note ends a little more quickly and the riff starts again. That last note of the sequence which I originally said is the length of SEVEN 8th notes, COULD have been 6-AND-A-HALF 8th notes.
Meaning the final note in the sequence would be a 16th note shorter.
The final bar could be a very fast 13/16.
4/4, 3/4, 3/4, 13/16
But I doubt they were doing that, because it would probably be too impractical (even for them).
I might make a segment about this on my podcast episode for next week. We’ll see.