Okay, I know you can read a review of it below, which gives you a plotline as well. But I came across this summary from the publisher, Fitzhenry & Whiteside, which is a nice straight line through the story.
Magnifico a novel by Victoria Miles (ages 11+)
Mariangela dreams of playing the piano, but when she arrives home from school one day to find a curious-looking suitcase in the living room, she has a sneaky suspicion that she can no longer hide from her 'some-a day inheritance' Waiting for her in the suitcase is her grandfather's old accordion. Her Nonna is thrilled, and Mariangela, well--she wanted a piano! ...instead she finds herself pulling the old, ugly accordion behind her on a red wagon--the only way she can get to her lessons--through the streets of Vancouver. How embarrassing! Even her handsome accordion teacher, all the more intriguing for his missing two fingers, can't inspire a passion in Mariangela for the instrument. What does interest her though, is his stories. Through her teacher's at times hair-raising tales of his journey, Mariangela reaches a new understanding of her own family's need to find a place in the new world while staying connected to their past in Italy.
Young readers of many backgrounds and experiences will find meaning in this touching story layered with a multitude of themes. Drawing on her own mother's accordion misadventures, Miles creates a rich portrait of Italian immigrant life in 1930s Vancouver and of a young girl struggling with timeless inner conflicts. Funny and sad, painful and inspiring, Magnifico is above all a deeply satisfying read.