りばーぶ (Reverb) is a vocal track from the Kotonoha Project (言ノ葉Project), a multimedia song series by MONACA, and debuted in maimai as an original commission for the PiNK version on December 9, 2015. The song was composed by Keiichi Okabe, the MONACA composer widely known for the NieR series soundtracks, and sung by Nana Takahashi, a regular MONACA collaborator whose voice gives the track its distinctive blend of playfulness and wistfulness. Lyrics were penned by uRy, who weaves imagery of daily déjà vu, echoing footsteps, and the classic Japanese children's game refrain "鬼さんこちら手の鳴るほうへ" ("Come this way, demon, to the sound of my hands") into a narrative about lingering connection and unspoken feelings. The title りばーぶ is a Japanese transliteration of "reverb" (残響), a word that echoes the song's central motif of resonance between two people. The track belongs to Chapter 2, Episode 2 of the Kotonoha Project's first season, and was later collected on the albums 言ノ葉遊戯 - 言ノ葉Project ORIGINAL SOUND TRACK - 第二章 and 言ノ葉プロジェクト ～詠唱集～. In maimai, りばーぶ's EXPERT chart was designed by mai-Star and the MASTER chart by rioN. The MASTER chart (level 11) is notable for its opening rotation pattern, which moves at a deliberately slower tempo than typical slides of its era, a detail highlighted in the in-game chart notes as effective practice for the PiNK version's new slide mechanics. Over the course of maimai DX updates, the song's in-game genre category shifted from ORIGINAL & JOYPOLIS to ORIGINAL, and eventually to maimai, reflecting the series' evolving classification system.