- "A wooden bass whose time in the limelight is up. Holds a grudge against the new bass on the block."
- — Battle Memory
- "As you can plainly see, I am a wooden bass. I'm still in my prime. But ever since the bass below showed up, I've been left to rot in this moldy-smelling attic. I'm filled with so much frustration. I'm gonna turn this frustration into violence and take my stress out on you guys! You're gonna be bawlin' your eyes out!"
- — Jealous Bass
When Lucky started using a new bass, the Jealous Bass was left in Club Titiboo's Attic, despite the fact that the instrument was still usable. Due to its frustration, the Jealous Bass apparently became sentient.
During Chapter 4, Lucas and Boney come across the abandoned bass, who takes its frustration out on the group and attacks, along with a Beaten Drum and a Gently Weeping Guitar. Once the Jealous Bass is defeated, Lucas and Boney can escape the Attic by jumping through the air duct into Lucky's room.
The Jealous Bass is capable of using Hypnosis α, along with a normal attack. For its most notable attack, it can initiate jam sessions with its "bandmates"; each of the instruments attack consecutively, with the Jealous Bass attacking twice. Its battle theme is Rock and Roll (Spicy), which can be changed by the Beaten Drum assisting it.
If Lucas defeats its comrades first, it will fly into a rage, causing its offense to rise. The Bass also resorts to solo jam sessions (a series of multiple strikes) as well.
Its battle sound is Battle Sound 13, which falls under three code numbers: 475 (regular attack) 476 (Smaaaash) and 477 (Miss). It is the only non-Titany enemy in the game (excluding the unused Aeolia's Table) to have this battle sound.