Harry and the Lady Next Door, written by Gene Zion, illustrated by Margaret Bloy Graham, HarperCollins, 1960.
I think this Harry book is even more fun and funny than the original Harry, The Dirty Dog. Harry has a problem -- the lady next door fancies herself an opera singer. She has all of the volume, but she is short on talent. Harry tries to solve his problems, with rather hilarious results, but, in the end, everything works out. There are actually four very short stories in this book, that all fit together to form a larger story.