Films must meet all of these requirements to be added:
1. Synchronized score and/or sound effects
2. Recorded dialogue for any/all portion(s) of the film (a "talkie")
3. Released prior to 1930
4. Exist in its entirety and not be "lost" (either in an archive somewhere or digitally online)

Films that can't be added because they are not on Letterboxd:
- Should a Girl Marry? (1928)
- The End of the Simpletons (1929)
- Hold Your Man (1929)
- In Old California (1929)
- Noisy Neighbors (1929)

Primarily sourced from here