According to Variety, Bella Heathcote, Christopher McDonald, Molly Price and Lisa Lampanelli are also in the cast.
The film is set in the suburbs of the 1960s. Gandolfini will play the father of a boy in a rock band, Magaro is cast as his son, and Garrett will play a composer and music producer.
Heathcote will play the boy's love interest, with McDonald cast as her father. Price will play the boy's father, and Lampanelli will portray his aunt.
Garrett, a three-time Emmy winner for his work on "Everybody Loves Raymond," appeared on Broadway in The Odd Couple. Magaro appeared in the Roundabout Underground production of Tigers Be Still.