Complex sentence: Lectures are coordinated on an ad hoc basis and, for the most part, have been held in an old funeral home in Williamsburg, though the series has also taken place in other non-traditional speaking venues, such as a former Catholic high school in Soho.
Split into simpler sentences: Lectures are coordinated on an ad hoc basis and have, for the most part, been held in an old funeral home in Williamsburg. The series has also taken place in other non-traditional speaking venues, such as a former Catholic high school in Soho.