Complex sentence: Haliday was an actor and founding member of the Brattle Theatre Company (BTC) based at the Brattle Theatre in Cambridge, Massachusetts; the BTC was an American version of England's Old Vic.
Split into simpler sentences: Haliday was an actor and founding member of the Brattle Theatre Company (BTC) based at the Brattle Theatre in Cambridge, Massachusetts,. The BTC was an American version of England's Old Vic.