Lost film soundtracks
Some films produced in 1926–1931 using the Vitaphone sound-on-disc system, in which the soundtrack is separate from the film, are now considered lost because the soundtrack discs were lost or destroyed, while the picture elements survive. Conversely, and more commonly, some early sound films survive only as sets of soundtrack discs, with the picture elements completely missing (e.g., 1930's The Man from Blankley's, starring John Barrymore) or surviving only in fragmentary form (e.g., Gold Diggers of Broadway (1929) and The Rogue Song (1930), two highly popular and profitable early musicals in two-color Technicolor).
Many stereophonic soundtracks from the early to mid-1950s that were either played in interlock on a 35 mm fullcoat magnetic reel or single-strip magnetic film (such as Fox's four-track magnetic, which became the standard of mag stereophonic sound) are now lost. Films such as House of Wax, The Caddy, The War of the Worlds, The 5,000 Fingers of Dr. T, and From Here to Eternity that were originally available with 3-track, magnetic sound are now available only with a monophonic optical soundtrack. The chemistry behind adhering magnetic particles to the tri-acetate film base eventually caused the autocatalytic breakdown of the film (vinegar syndrome). As long as studios had a monaural optical negative that could be printed, studio executives felt no need to preserve the stereophonic versions of the soundtracks.