His next compositions had their roots in the themes from the Holocaust, but he soon felt that the combination of political agitprop and the avantgarde idiom to be an artistic dead end and his style moved on to explore subtle sound nuances, inspired by the piano technique of his friend, the pianist Maurizio Pollini, to whom he had dedicated several works from this creative period. The exploration of the individual sound became the centre of throught during this creative period, so much so that the compositions often move on the edge of audiblity; literary and musical quotations from various sources, ranging from Hoelderlin to Verdi, form isolated tonal islands which are the result of the greatest possible concentration of the innumerable sources of inspiration. Even his most mature works follow this concept so that they lack an explicit story; one might speak of an ’invisible theatre’, the ideas of which are musicalized and which, in itself, takes place only inside the listener himself.