The Fandom Post is reporting that Shout! Factory has added the Sound! Euphonium: The Movie – May The Melody Reach You! anime film for streaming on Amazon. It’s only available to Prime members with no purchasing options available. The film is available with the original Japanese and English subtitles.
The story of the film is described as:
Autumn is in the air as the Kitauji High School concert band prepares for the National Competition. The band hears troubling news that Asuka Tanaka, vice president of the club and one of the key euphonium players in the band, may quit. Asuka is beautiful and charismatic and everyone relies on her, but she also has a cool side and never reveals her true self. Kumiko doesn’t get along with Asuka initially, but her feelings change when she learns that Asuka may actually drop out. Asuka has feelings about the euphonium that she cannot tell anyone else…
Source: The Fandom Post