The piano soundboard is the heart of the instrument. Its material and geometry affect the sound quality, determine the available dynamic range and colouring of the produced sound. The proper construction and the carefully selected and processed materials guarantee the reliability and durability of the instrument. The soundboard is traditionally built from solid music wood, but various alternative materials have also been experienced with. Nowadays manufactured composites are emerging of two motives: the available resources of high-quality music woods are shrinking, and the manufacturing and invention of traditional soundboards need plenty of time. According to experiments on other instruments (e.g. guitars), natural fibre composites seem to be ideal substitutes: they are of aesthetically pleasing texture, and the design and production process is supported by digital solutions. The question is, is it possible to meet the modal behaviour of the original soundboard by careful parameter selection. In this paper, we present a possible systematic estimation chain to determine the required effective parameters of composite sandwich panels capable to substitute wooden ribbed soundboards. The estimation results in hypothetical parameters, the physical aspects of their realisation have not been investigated yet. The results are demonstrated on a piano soundboard as a numerical example.