While some sellers classify a piano baby as a doll, these were actually decorative objects rather than playthings for children. During the Victorian era, homespun music was an entertainment staple. So yes, these precious and often life-like figures really were designed to decorate pianos in parlors of the day.
The piano babies made by Heubach range in size from small at about 5-inches to 12-inches or so for the rare larger examples. They can be posed laying, crawling or sitting, and almost always have a sweet look about them in contrast to Heubach's character dolls that can have quite solemn or even angry facial expressions. Some of them are clothed more fully than others, the the one wearing a bonnet in the photo above.
In the early 1900s the company began making glazed figurines as well, including a number of nicely crafted examples depicting various dog breeds.
Learn about Heubach Christmas décor on page 5.