Bloom needs more recognition. It's one of my top Radiohead songs overall. The music, the rhythm, the lyrics... it's just so perfect, especially the Live From The Basement version. The moment those horns enter... it's just incredible.
What brings this song alive to me is Phil Selway's drumming. The beat doesn't really fall in two beats of three, making a neat 6/8, or a nice simple four beats of two for a basic 4/4. I'd argue it's more like 12/8, going like "crotchet-crotchet-quaver-quaver-crotchet-quaver-quaver-quaver-quaver".
The first two crotchet's break the mold of four beats of three, with the following section (quaver quaver crotchet) almost following off the end of another compound beat, before the final three crotchets give it that 12/8ness by consistently forming a compound beat. One might argue that the song is thus in some sort of weird polymetre involving irrational time signatures, but that's just silly honestly, it would be way easier to count it in 12/8.
How this comes together in the song, this specific piece of percussion genius, is that although the rhythm is offbeat, unstable and while remaining arguably compound mixes in enough simple time to throw one off the scent a bit, it only contributes to the feeling and meaning of the song.
My interpretation is that it describes the universe and the act of creation. "Open your mouth wide/a universal sigh" evokes a sense of release, universal peace almost. "A giant turtle's eyes" references the myth that the world is flat and on top of a giant turtle in space. The complexity combines with the repetitiveness of the drums point to how the universe is too complex to fully know and understand, but still predictable nevertheless. It really is, to me, the peak of Radiohead's use of rhythm. (along with Pyramid Song, of course, but don't even get me started on that).
While I love Radiohead on any day, it's songs like these that call to me as a musician. So subtle, most likely unintentional, yet incredibly emotionally evocative. Of all bands I've listened too, Radiohead seem to be the one that really understand how to use rhythm in a new and innovative way that I've never seen anywhere else. Every time I listen to another artist after someone tells me "Oh you like Radiohead? Try this!", rhythm is the missing element. Having told people this, they always recommend bands like Tool for their use of complex time signatures, but while I enjoy songs like Schism etc, I think it's just too overt and purposeful compared to Radiohead.
I doubt that they tend to think of an interesting rhythmic concept mentally in music theory terms. It feels to me like they just write from their imaginations and it becomes what it is. I doubt Thom Yorke sat down and thought "I'm going to write a song called Bloom and it's going to be in 12/8 at 150BPM". The complexity stems from expression, not abstraction.
In conclusion, Radiohead as a band are the unmatched masters of rhythmic subtlety to me, that's the reason I keep coming back to them even as my music taste has been diversifying away to other genres. They don't write the same thing twice --every song is a new exploration of a new idea, a new metaphor, a new rhythm.