What should I fill them with? All answers welcome. Budget-friendly answers preferred. These will be open-back, porous traps covered with discount fabric. Cheers!

Hey everyone! If you have a sec, I'd love to get some feedback on a new song. I'm especially wondering if you are hearing any harsh resonances with the vocal in the beginning? And just general feedback about how things are sitting together! Thanks! https://on.soundcloud.com/lELeqZyhhSM55y8kMb

One thing I've learned from "How to be a good film-maker's" analyse reference tracks. I wanted to analyse electronic music for this task, and while some tracks I could definitely conceptualise as having sections, some feel a lot more like they are made entirely out of grooves or a single evolving groove; or even, a groove mutated with bridges and drops all the way down the line. One example is "Is U" by Overmono. Structure feels very arbitrary and loose. It feels driven by the evolution of bridges leading into subtle drops. I'm really into it, it gives me a sense of being lost in time. I think the end result is I need to analyse 50 more tracks like it before I could generalise about this structure, have intuition about what the actual sections are called, or distil any really significant abstractions about the structure. But, if I knew the planned structure, I bet that would define or dictate in some sense how the track evolves so it would be interesting to see if it's just an organic process or something more modular and well defined. If anyone knows what it looks like inside an Overmono project with marker labels and arrangement notes I'd be really keen to hear about it and learn how they conceptualise structure on a track like "Is U".