Three years ago, San Diego Repertory Theatre audiences were the first in the country to see Hershey Felder’s play with music about the famed Russian composer Pyotr Ilyich Tchaikovsky. On Sunday, Rep audiences revisited the play in a livecast from Florence, Italy, where Felder has set up a streaming production company while he waits out the pandemic. Just as the play’s delivery format has changed, so has the play itself. The Canadian playwright/pianist/actor/producer turned “Hershey Felder: Tchaikovsky” into a filmlike study of the emotionally tortured composer’s life, rather than the traditional direct address to the audience where he plays both composer and narrator.