Algorithmic music and computer-aided composition often pose problems of form organisation. The reproduction of the vertical (harmonic) and horizontal (melodic) structures must be integrated into larger structures building the form of the composition. The mathematically constructed structure of musical work allows to reproduce the algorithm of the form building at the level of its creation. The analysis of different works by the Estonian composer Arvo Párt shows that his creativity process is based on strict mathematical logic of construction. This logic combined with the tinntinnabuli technique of composition, provides ideal material for the creation of these algorithms. Programming environments such as OpenMusic allow to create models for the reproduction and reconstruction of musical compositions based on the analysis of the composer’s creative process. In this article we show such models created for the generation of Arvo Párt’s music, including form structure organisation, based on algorithms conceived from the analysis of his works ( Tabula Rasa, Mein Weg, Spiegel im Spiegel and Fratres).