[1] It is considered one of the most influential works written in the twentieth century for the classical guitar.
[2] Julian Bream premiered the piece on 12 June 1964.
[3] The piece is a sort of reverse theme & variations (it is called "Reflections") on Come Heavy Sleepe from John Dowland's First Book of Songs (1597).
Each variation contains fragments of Dowland's theme, most notably the use of the perfect fourth interval.
The variations move progressively closer to the Dowland song concluding the piece.