Complex sentence: The Redlands Society, which is informal society exists to encourage and improve music, art and drama at Wantage, which in 1960s was responsible for a Folk Music Club and a jazz band.
Split into simpler sentences: The Redlands Society, which is informal society exists to encourage and improve music, art and drama at Wantage. In the 1960s it was responsible for a Folk Music Club and a jazz band.