Complex sentence: Such structures provided civic offices, a council chamber and a large auditorium in one building and often had a clocktower and usually an organ in the large auditorium and often a smaller auditorium for chamber music.
Split into simpler sentences: Such structures provided civic offices, a council chamber, and a large auditorium in one building and often had a clocktower. Most had an organ in the large auditorium, and often a smaller auditorium for chamber music.