As with previous releases, the album features music of numerous genres, including psychedelia, progressive rock, heavy metal and synth-pop, as well as the band's first experiments with hip hop.

During the production of the 2019 album Fishing for Fishies, the band King Gizzard & the Lizard Wizard recorded at a house owned by members of Tropical Fuck Storm.

A limited-edition vinyl, titled Hat Jam, was also released featuring both "The Dripping Tap" and Satanic Slumber Party.

However, the music in the clip did not end up appearing anywhere on the record, and instead was an extract of the then unreleased Omnium Gatherum track "Magenta Mountain".

[16] Omnium Gatherum is an album that sees the band hopping between numerous different genres, including psychedelia, progressive rock, heavy metal, synth-pop, folk, jazz, R&B, and soul.

[26][20][23] "Sadie Sorceress" and "The Grim Reaper" introduce rap elements to the King Gizzard sound, with the latter incorporating microtonality and psychedelia.

[20][22] "The Garden Goblin" is a twee lo-fi bedroom-prog and psych-pop song, and "Evilest Man" features political acid rock and callbacks to the track "Cyboogie" from the 2019 album Fishing for Fishies.

David Weinberg, writing for Glide Magazine in 2023, wrote, "the unique and august qualities of Omnium Gatherum warrant .

"[25] Loud and Quiet's Jack Doherty criticized the album's disparate styles, claiming that it "crumbles under its inability to surprise, leaving us with the sound of a band with nowhere left to go.

"[18] Under the Radar contributor Kyle Kersey wrote "Taken as a complete album experience, it's a little too all over the place to measure up to their most focused work, and its robust length is pretty intimidating.