In an Acoustic Piano, the tightly wound strings are generate from steel. However, it’s the wooden soundboard that translates their energy into a rich and resonant sound.
If it were just a matter of projecting and amplifying the sound produced by hammers hitting the strings, though other materials could potentially be more efficient, the resulting sound would be too metallic.
The soundboard material selectively filters out the higher harmonic components, retaining only the musical components that are musical and pleasing to our ears. This transformation results in a richer and more resonant tone.
What makes the spruce woods, especially the Italian spruce from Italy’s Val di Fiemme region so popular as soundboard materials is their unique ability to absorb higher tones more effectively only transmitting the sounds perceived as rich and mellow.
This wood is exceptionally elastic, enhancing sound transmission, while its naturally occurring lymphatic channels resemble miniature organ pipes, creating a beautiful resonance. That's why Italian spruce trees are felled during the waning moon, typically between October and November, when there's less sap within the trunk.
Indeed, the legendary violin luthier Stradivari and the Cremonese luthiers, whose instruments epitomize the pinnacle of musicality, utilize Italian spruce.
Legend has it that Stradivari himself wandered through the forests seeking the most suitable trees for crafting his violins: centuries-old spruces whose wood, owing to its exceptional capacity for “resonance”, provided the ideal raw material for his soundboards.