The combination of Lutosławski's aleatory techniques and his harmonic discoveries allowed him to build up complex musical textures. According to Bodman Rae, in his later works Lutosławski evolved a more mobile, simpler, harmonic style, in which less of the music is played with an "ad libitum" coordination. This development first appeared in the brief "Epitaph" for oboe and piano, around the time Lutosławski was struggling to find the technical means to complete his Third Symphony. In chamber works for just two instrumentalists the scope for aleatory counterpoint and dense harmonies is significantly less than for orchestra, but these developments also influenced his orchestral style in late works including the Piano Concerto, "Chantefleurs et Chantefables", "Chain 2" and the "Fourth Symphony", which require mostly conventional coordination.