They were two brothers who were both in jazz but so different that they could not work together. At least till after the death of their father which brought them together for the production of the concerto of Janet Blair's husband's concerto, and yet under the conducting of a third party. But when they were together they made miracles particularly in their trombone-saxophone duets. The film shows how difficult life was for jazzmen at the beginning, but also how the radio transformed the spreading of this music, and then this spreading was amplified by the recording of their music on records. Jazz is typically American in its use of rhythm and new instruments like the saxophone, and old instruments like the clarinet and the trombone which are perfectly transformed in the process. But most of all, jazz would not have existed if they had not used the radio and records to reach the wider public. Jazz is the first music of modern ages. It was also a great success because it expresses life in our modern times of cars, factories, machines, industrialisation and mechanisation. People expected a new type of music in phase with this new life and jazz provided it to them. This film is thus both historically and humanly true and sensitive.