What makes a music piece difficult (or easy) from the point of view of the composer, the performer, or the listener? The answer, as illustrated by the oeuvres of Schumann, Debussy, Bartók and Ligeti, among others, is far from clear. A piece may be simple in terms of playing technique, but musically demanding, or vice versa: the energy invested by the performer is often not in direct proportion to the significance of the listening experience. Nevertheless – if we may bring forward the lessons of the evening – the greatest composers wrote great music even in their smallest pieces.