"Pseudo" polyrhythms in Mvmt. 1 of Rachmaninoff's Second Sonata

[hovva]

Hello all,
I am currently learning the first movement to Rachmaninoff's second sonata. I'm working on a very interesting passage that involves what I think can be best described as pseudo-polyrhythms. The passage is written in 6/8, but there are measures that are comprised of octuplets in the right hand and quadruplets in the left hand, so the rhythm is "de facto" 8:4 (2:1), but "de jure" 8:4:3 where 3 is the subdivisions dictated by the time signature. So although my hands aren't playing a polyrhythm, the notes are polyrhythmic with respect to the beat, hence the name "pseudo". I'm very curious about these rhythms. Is there an official name for them? What other pieces do they occur in? How does one go about practicing them? I've been trying practicing this with a metronome set to 6/8, but I find it difficult to play non-conflicting rhythms with a conflicting metronome for some reason. I'm used to playing most polyrhythms, but this poses a challenge I haven't faced before. Lately, I've been cheating by converting my desired BPM from 6/8 to its equivalent in 8/8. I'm not sure that a strict pulse is necessary for this passage in the long run, so I feel this is an acceptable compromise, but I'm curious as to what you all think.

[soultrap]

I consider this passage to be a combination of a 3/4 bar and a 4/4 bar (with syncopated beats), if we're talking rhythms. I don't believe it's as big as a deal as some other passages, where rhythm is much more important. The undervoice polyphony right before the coda, and before the transition towards the development is more rhythmically demanding, as those parts require a strict mentality of triplets. It's much easier to get lost in those areas than the section you mentioned.

[comma]

As you said, this is not a truly polyrhythmic passage. Set your metronome to 1 beat per half a bar (3/8) and it shouldn’t be a problem.