As Miles Davis' classic Bitches Brew celebrates its 50th anniversary, Ben Cardew talks to Barcelona film maker Balthazar Klarwein about his father - artist Mati Klarwein - who painted the cover of that album, as well as records from Santana, Buddy Miles, Jon Hassell and Jam & Spoon.

'Bitches Brew', oil on canvas, Mati Klarwein 1970 © Klarwein Family