The title, actually the subtitle, was something like "OR, The Things in [girl's name, I think it might have been Susan]'s Piano."  It was about a girl who was bad at playing the piano, maybe willfully from refusing to practice, and inside the piano were monsters who were hurt or injured or horrified or angry or something, by her bad playing.  They may have been musical notes come to life.  It was a picture book in my elementary school library, so it was published before 1982.  Probably in the 70s.  It was sort of psychedelic and the characters were almost ugly, deliberately so.  I remember lots of teeth in big mouths.

Picture book from 1980’s (?) about a preschool aged child’s relationship with a baby sibling. Illustrations depict a messy, hippy-ish house, perhaps in Vermont, with a frumpy, gentle mom. Specific pictures include: the outdoors with a steep path leading down to the home with baby in stroller and sibling walking; hall entryway with pegs on the wall where coats are hanging and shoes & boots scattered on the floor; frazzled mom cooking with baby on her hip crying and sibling playing on the floor; sibling helping button clothes on baby and maybe attempting to tie own shoe; sibling feeling tender toward baby in their shared bedroom and maybe text anticipating baby being old enough to play. Illustrations have lots of detail about the environment, which is a warm but messy home, e.g. baby socks on the floor, toys scattered, kitchen counters cluttered, etc. Aesthetic of home is alternative, earthy.

I had a book as a child. Had to be in the early 80s. It was a book with pictures and words. A whole story from what I can remember. It was about a little boy that wanted to play outside but it was raining. His mother wouldn’t let him play outside and he built a train out of furniture in the house and played train all day until the sun came back out