"Where there is devotional music, God is always at hand with His gracious presence."

Even to sceptical and agnostic minds, Bach's B minor Mass radiates a recognisable and powerful spirituality, one that does not rely on credal orthodoxy, odd though that might appear. His art celebrates the fundamental sanctity of life, an awareness of the divine and a transcendent dimensjon as a fact of human existence.

It is by anchoring it in our time that we re-connect with the timeless fertility of Bach's imagination.

He saw both the essence and practice of music as religious, and understood that the more perfectly a composition is realised, both conceptually and throught performance, the more God is immanent in the music. 'NB', he wrote in the margin of his copy of Abraham Calov's Bible commentary: 'Where there is devotional music, God with his grace is always present.'

But it is Bach, making music in the Castle of Heaven, who gives us the voice of God - in human form. He is the one who blazes a trail, showing us how to overcome our imperfections through the perfections of his music: to make divine things human and human things divine.

These are the tones of someone attuned to the cycles of nature and the changing seasons, sensitive to the raw physicality of life, but buoyed up by the prospect of a better afterlife spent in the company of angels and angelic musicans. It is this that has prompted the book's title, describing both the physical reality - the 'Himmelsburg' in Weimar was Bach's workplace for nine formative years - and providing a metaphor for the seat of divinely inspired music.