In Greek mythology, Achlys ( Ἀχλύς "mist") was, according to some ancient cosmogonies, the eternal Night (perhaps the Mist of Death, which fell before the eyes preceding death), and the first created being which existed even before Chaos.

This piece is in the wonderfully intense and mournful sounding ancient Greek Hypodorian Mode (misnamed the 'Aeolian' mode in the Middle Ages, this mode, heard here in authentically pure just intonation, is the equivalent intervals as A-A on the white notes of the piano). This ancient Greek mode, the basis of our modern minor scales is also sometimes referred to as the 'Natural Minor Scale'. The use of just intonation in this piece further enhances the distinctive emotional effect of this mode.