The techniques and aesthetic of Xenakis's music have been widely discussed in books and articles—many by the composer himself. These issues belong to the ‘outside time’ characteristics of music which Xenakis has defined in his article ‘Towards a Metamusic’ (TEMPO 93). So far, however, there has been little or no detailed discussion of the ‘inside time’ aspect of his music, namely the problems relating to its performance, although it is generally known that many of his works—especially those where solo players are involved, such as Nomos Alpha, Mikka, Eonta, Herma, Evryali, Synaphai-Connexites—are exceptionally difficult to play. These problems are important and must be solved not only for the sake of satisfactory performances of Xenakis's music, but also because they raise wider questions concerning the further exploration of instrumental technique.