The title of this comes from Friedrich Schiller’s Ode to Joy, on which part of Beethoven's Ninth Symphony is based. The film is a seven-year flashback and we learn of the accidental death of the protagonist's wife at the beginning of the film. Stig (Stig Olin) and Marta (Maj-Britt Nilsson) play violin in an orchestra directed by Sönderby (Victor Sjöström*) and soon marry with children. It's the huge ambitions of Stig that are the problem, and he wants to be a soloist, although Sönderby knows that this will not be possible. Then Stig starts becoming involved with Nelly (Margit Carlqvist). This is far from being Bergman's best film, and I think it's mainly the melodrama that spoils it, although some may consider that the music redeems it.
*Sjöström (1879-1960) was a noted film director who also starred in Bergman's Wild Strawberries.