While it sounds pretty weird, this was standard practice back in the day. According to Patrick Miller in his article “Music and the Silent Film,” Hollywood director D.W. Griffith enlisted a brass band to encourage extras during the battle sequences of his 1916 three-and-a-half-hour epic, Intolerance. Fellow director King Vidor often relied on opera recordings to get his actors in the right headspace.
At Atlas Obscura, Nolan Moore shares the unsung story of Danny Borzage, the accordionist who provided the emotional motivations for actors’ performances in silent-era Hollywood.