Bryyo Seed Boss is a frantic battle theme in Metroid Prime 3: Corruption. It is heard during the battle with Mogenar and primarily consists of synthesized instruments, including percussion and percussive beats.
While not a direct remix, the theme resembles Big Boss Confrontation BGM (Kraid, Crocomire, Phantoon), Kraid's battle theme from Super Metroid and Metroid: Zero Mission, which is shared by Crocomire, Phantoon and the Big Metroid in Super Metroid. It should be noted that Mogenar resembles Kraid himself, as well. Bryyo Seed Boss is the only Phazon Core guardian battle theme to not be available in the Soundtrack Gallery in the original version of Corruption, or Metroid Prime Trilogy re-release. It was composed by Kenji Yamamoto, Minako Hamano, and Masaru Tajima.
The theme can be heard here.