Olli Mustonen, the Finnish pianist, composer and conductor, is at home on all concert stages of the world. Recently, he has mainly composed chamber music works. His Quartetto with the allusive movement headings 'Quasi una passacaglia' and 'Es muss sein' provides a wide sound spectrum evolving due to the possible combinations of instruments. According to the traditional pattern, calm and emotional passages alternate with extremely lively and virtuoso passages. The piece requires high technical skills, has an immediate catchy effect and is suitable for any concert programme.