Japan's Buddhist temple bells
There are thousands of Buddhist temples scattered across Japan and most have huge bronze bells - bonshou - which are cherished and revered.
This week's Heart and Soul captures the physical and symbolic power of these bells, and they are awesome, some weighing more than 30 tons. They are struck on the side by a suspended tree trunk, swung by teams of up to 20 monks. Some are ancient - one bell featured was cast in the year 752.
Casting a large bell in bronze is a perilous business with a high chance of failure, and Ikko Iwasawa who runs the foundry which cast the largest bell in Japan explains the mystery and ritual as a new bell is being cast.
The head priest of Rengein Monastery, whose bell can be heard 30 miles away, reveals their spiritual meaning and the impact they have on people.
The programme weaves Japanese haiku poems and interviews with the sounds of famous bells in the cities and countryside, each with its unique voice.
Photograph of Japanese bonshou bell copyright Getty Images.