Quartet Theme [Reborn] is a modern arrangement of the stage 1 BGM from SEGA's 1986 four-player arcade action game Quartet, reimagined for the rhythm game stage by COSIO (Hirokazu Koshio) of TAITO's in-house ZUNTATA sound team. The original composition, a funk-driven piece by Katsuhiro Hayashi, credited as Funky.K.H, is transformed into a bright, disco-house arrangement built for danceability. COSIO opens the track with a rising synth bend that deliberately echoes the original's iconic intro, then steers the rest into late-80s club territory, a stylistic choice inspired by Quartet's 1986 release year. The song entered maimai through an unusual cross-company partnership between SEGA and TAITO, debuting simultaneously in maimai PLUS and GROOVE COASTER ZERO on February 20, 2013. Its in-game PV pays direct homage to the source material: MARY, one of the four playable characters from the original Quartet, runs and flies through pixel-art levels before diving into a goal door, a faithful nod to the original's stage-clear sequence. The track's in-game genre classification has shifted multiple times across maimai versions (cycling through ANIME & GAME, GAME, SEGA, ORIGINAL, and finally settling at GAME & VARIETY), reflecting its unusual status as a SEGA game theme arranged by a TAITO musician. A full-length edition appears on the maimai SEGA Sounds Vol.3 soundtrack, and a separate VOCALOID remix, 多重未来のカルテット-Quartet Theme- by KUSEMONO and SWANTONE featuring Hatsune Miku, was later featured in HATSUNE MIKU: Project DIVA Arcade Future Tone.