Science-fiction that centres on cutting-edge developments in physics is referred to as ‘hard’; contemporary music of the most modernist stance is also referred to as ‘hard’. Spaniard Hector Parra’s extraordinary opera Hypermusic Prologue with a libretto written by practising string-theorist Lisa Randall about higher-dimensional astrophysics, recently issued on the Kairos label, is ‘hard’ in both senses. It is definitely not recommended for anyone who is uncomfortable with Ferneyhough, Lachenmann, or Xenakis, or who doesn’t follow the fashions of Theories of Everything. But for those that relish such challenging music and ideas—and even those who are prepared to take the leap—this is a core work. The music contrasts luminous, flickering ensemble orchestration of great beauty with strikingly lyrical sung and vocalised lines, making the music feel less ‘alien’ than might be expected. The disc comes in a box with a full-colour leaflet that, uniquely in my experience, contains an appendix of mathematical-physics ‘referents’, to assist in comprehending the work, plus a second disc containing an explanatory interview with composer and librettist (in english—fortunately). I found myself enjoying this dense work immensely; it is an indispensible purchase for anyone who, like me, regards High Modernism as the one expressively uncompromised music still being created.