I read the book around 1978-1983. It was a fantasy with a child who stayed with family and went into the woods and found a passage to a fantasy world of fairies which she ended up traveling to. The book had a title that was a play on Maestro or some other musical name. The cover of the book was brownish red with the face of one of the fairies. The face was very large and very round(side-wise oval) and with a very wide mouth. I was between 9-12 yo when I read it but this is what I remember.