Episode 2/5. In 1705, the 20-year-old Johann Sebastian Bach set off from his home in Arnstadt to walk 250 miles to Lübeck, there to meet his hero, the composer and organist Dietrich Buxtehude.

In the second of five "slow-radio" walks in which writer Horatio Clare searches for his footsteps - and his ghost - the putative route takes him into the Harz Mountains and up to its highest point, the Brocken Summit.