Have you ever wondered why grand pianos have these holes in their plate?
Piano plates are made of cast iron, and as such are forged at very high temperatures. These “cooling holes” are strategically placed in the plate to break up large contiguous areas of cast metal so that the entire plate can cool more evenly and quickly, avoiding warping and cracking.
As cool as it would be, they are unfortunately not “subwoofers” or “sounding holes” and having more of them does not necessarily make your piano better. There is minimal impact on sound and that is not the purpose of the holes.
What IS cool though, is that various manufacturers trim and decorate the holes in different ways, and it can be a unique identifying element of a piano’s history! This one is a 1926 Steinway L baby grand.