Music from another time; Plains Song, by Wright Morris. New York: Harper & Row. $9.95.

This is a beautiful, subtle novel that accomplishes the rare effect of presenting history from the inside out. Rather than measure gigantic social changes, the weight with which earth-shaking events rests on individuals (John Steinbeck's "The Grapes of Wrath" comes to mind), Wright Morris carefully records the quiet equivocations of the human heart.

"Plains song" is a history of the Atkins family from the early 1900s to the 1970s. More particularly, it is the story of Cora Atkins, whose life frames the book, and the other Atkins women.

Cora is sent west at age 20 to live with an uncle's family in Ohio. She soon receives a proposal of marriage from Emerson Atkins, who has come from east to pick up supplies for the Nebraska farm he and his brother Orion have claimed. Cora hesitates only slightly before she accepts.

Cora and Emerson have a daughter, Beulah Madge. Orion marries and his wife, Belle, gives him a daughter, Sharon Rose, and a second daughter who dies as an infant, before Belle herself dies in childbirth with the third daughter, Fayrene.

In some cases, history becomes dramatic only in the retelling, in the accumulation of statistics -- lives lost, acres settled; time bestows significance on the ordinary by obscuring details and leaving only outlines, homogeneous lumps of accomplishment or failure. But there are few dates or landmarks in "Plains Song." Only occasionally does the world intrude on these people's lives, sometimes passing like a brief, ill wind, sometimes leaving a permanent scar. Morris writes from the perspective people have on their own times: the uncertainty and confusion, the impossibility of knowing the future, or understanding the present, that we may experience in our own lives.

"Is the past a story we are persuaded to believe, in the teeth of the life we endure at the present?" Morris asks on the first page. The past he reveals is one with few embellishments, something almost unexpected. These people don't say much, there's little reason for their minds to wander outside their immediate world. It is not so much in actions or words that Morris's characters establish themselves, as in the long silences between words and deeds.

Morris examines his characters' every small gesture, refusing to make any statement that would let our feelings rest on one side or the other. He shows us Cora as a new wife, walking beside the wagon, her skirt sweeping the prairie grass, sometimes pressing flowers in a book -- and he also shows us Cora as an old woman: "She was never spry, comforting or twinkling, and the young are reluctant to call her Grandma to her face. Nor do they raise their faces to be kissed. Not that she is cold, unloving, or insensible. She is implacable."

With children and then grandchildren, the novel becomes inevitably more complex and diffuse. Sharon Rose breaks from home and establishes an independent, solitary, life in the East. Finally, she becomes the book's focus: the one Atkins of her generation who doesn't marry, she breaks tradition, but perhaps feels the heritage of her past more heavily than any of the others. At the book's end things get a little too hard to follow, and a woman's convention becomes too much of an overt statement, too much a theme instead of a setting. But it's a small complaint.

As the title suggests, this is a melody without accompaniment, music of the simplest and most beautiful kind. Perhaps it is because Morris sketches his characters so sparingly that they seem so indelible.They are such a real presence that it's hard to think they haven't actually lived. Somehow, I'm convinced they have, a hundred times over.