I'm fairly certain that Fantasia (1940) was the first commercially released film to feature a multichannel soundtrack (at least at limited roadshow engagements). The "FantaSound" system utilized three screen channels as well as auditorium speakers (although I'm not exactly sure whether there was a discrete surround channel or whether there was selective panning of one of the three main channels). The next commercial release I'm aware of that featured a multichannel soundtrack was This is Cinerama (1952). Does anybody know whether there were any films released after Fantasia and before This is Cinerama that had multichannel soundtracks? Also, does anyone know how many non-CinemaScope 35mm films during the 1950's were presented with multichannel soundtracks? I was certainly aware that some CinemaScope films had a magnetic four channel soundtrack, but I was surprised to learn that From Here to Eternity used a discrete three channel soundtrack for large venues.