電車で電車でOPA!OPA!OPA! -GMT mashup- is a crossover mashup born from the Game Music Triangle (GMT) collaboration, a three-way initiative between TAITO's Groove Coaster, SEGA's maimai, and Bandai Namco's Taiko no Tatsujin. As the second entry in that project, the track splices together two classic arcade game themes: the train-conductor chant "Densha de Densha de GO!GO!GO!" from TAITO's Densha de GO! series and the buoyant melody of "OPA-OPA" from SEGA's Fantasy Zone. Composer Yuji Masubuchi, known inside Bandai Namco for his prolific, offbeat Taiko no Tatsujin arrangements, built the sound around a self-imposed gimmick: a fictional 30‑year‑old sound chip combining a C30 waveform generator, an AY‑3‑8910 PSG, and dual MSM6258 ADPCM channels panned left, center, and right. The result is a deliberately lo‑fi, retro‑futurist audio palette that wraps the Densha de GO! vocal hook in chirping PSG arpeggios and lets the Fantasy Zone sections burst into full chorus. Lyrically, the song follows a Japanese commuter's morning grind, the 5:30 AM Saikyo Line departure, the Musashi‑Kosugi stall, the scramble for a spot on the packed express, drawn from the Densha de GO! song tradition. Masubuchi repurposed vocal stems from the original 1997 studio recording and from the GMT remix, degraded them to sound like vintage ADPCM, then had Bandai Namco staff sing the Fantasy Zone vocal parts after realizing the existing OPA-OPA lyrics happened to reference crowded train cars. That thematic serendipity gives the mashup a narrative coherence beyond its musical fusion. In maimai, the song debuted on May 8, 2014 as part of the GreeN PLUS update. Its Master chart, designed by 譜面-100号, is notably slide‑heavy, 169 Slide notes out of 572 total, and has been re‑levelled upward across multiple versions, settling at 13.8 (13+). The Expert chart, penned by mai-Star, anchors at 11.6 (11+). The song was originally filed under a COLLABO genre tag in early maimai versions before being moved to GAME & VARIETY (ゲーム＆バラエティ).