Azul, the evocative Spanish word for ‘blue’, is the title of the contemplative cello concerto by Argentinian composer Osvaldo Golijov. It forms the centrepiece of this album by Brooklyn-based orchestral collective The Knights, which takes the skies as its theme. Today’s most celebrated cellist, Yo-Yo Ma, joins The Knights for the concerto and for a transcription of Dvořák’s poignant ‘Song to the Moon’. The diverse and fascinating programme is completed with music by the contemporary Iranian composer Siamak Aghae, visionary avant-gardist Karlheinz Stockhausen and eclectic singer-songwriter Sufjan Stevens.