Explanation of the title: ''Moros'' = Fate, death. ''Morsima'' = that which comes from Fate. ''Amorsima'' (''a'' being the negative particle) = that which does not come from Fate. The work is the result of the same programme as for ST/10 but for a different combination of instruments. The work was calculated by the electronic brain 7090 IDM in Paris in obedience to a special stochastic (probabilist) ''programme'' devised by Xenakis. This ''programme'' was derived from the thesis of ''Minimum rules of Composition'', which had already been formulated in ''Achorripsis'', but it was not until four years later that it became possible to have it ''mechanised'' at IBM-France. The ''programme'' is a complex of stochastic laws which the composer had been introducing into musical composition for a number of years. He orders the electronic brain to define all the sounds of a sequence, previously calculated, one after the other. First, the time of its occurrence, next its kind of timbre (arco, piz zicato, glissando, etc.), its instrument, its pitch, the gradient of its glissando where that occurs, the duration and dynamic of the emission of sound.