Lutosławski's development as a composer progressed from a relatively traditional tonal language to a more radical style, which is characterised by a ''distinctly original and increasingly refined aleatory dimension". 1 Lutoslawski, who was born in 1913, has composed works for most genres: orchestral music, chamber music, songs, music for piano, film and theatre music, as well as a number of pedagogical works for children and amateurs. It is, however, his orchestral, as well as some of his vocal-instrumental works, which most clearly demonstrate the development of his musical language.From his earliest well-known orchestral work, Symphonic Variations (1936-38) up to the Concerto for Orchestra (1951-54), Lutoslawski's work moved within the boundaries of an extended tonality.The Five songs on texts of Kazimiera Iłłakowicz (1956-57) for mezzo-soprano and piano,* Muzyka żalobna (late 1954-58), and Three Postludes (1958-60; revised 1963) formed the first stage in the development of a "new" musical language. This does not mean that Lutosławski has made a total break from his earlier works. There are fundamental elements in his writing, which remain basically independent of changes in his stylistic direction. Periodically they do, however, undergo modification to a greater or lesser degree. The differences between one work and the next have never seemed to be very great, but should one compare Jeux vénitiens (1960-61) to Les espaces du sommeil (1975), Novelette (1978-79), or the Third Symphony (1974?-83) it is not difficult to appreciate how far this composer's musical language has developed. Lutoslawski's own view: "... You must have heard the saying that writers write the same novel throughout their lives. That is true. If you compare the works of a composer written in different periods of his life, you will always find the same man behind them." 2 The three works mentioned earlier, namely the Iłłakowicz songs, Muzyka zalobna, and the three Postludes reveal, "one by one, individual traits of style which would finally coalesce to produce the mature style of the 1960s". 3 As regards the Iłłakowicz songs Stucky notes that: "The importance of this work in Lutosławski's development is often overlooked .... But in the critical matter of harmonic organisation it is the Iłłakowicz songs which mark the turning-point by exhibiting the salient feature of Lutosławski's mature harmonic practice: the consistent use of harmonic aggregates comprising all twelve pitch classes, employed for their expressive and coloristic values." 4 * A version for mezzo-soprano and chamber orchestra followed in 1958.