Thanks to Eduardo I got a picture of the El indolo del Tango movie. This film was released in 1949.
The film was directed by Héctor Canzioni and, although it contains a lot of music like vocals of Julio Martel, it is not a very intersting comedy. Oscar only plays in one scene where he dances and sings in his typically Aleman way. ( Part of ) this scene is to found on the Django Music sites and if you have the latest Media player you can view this scene on that site.
Oscar Aleman in El Idolo del Tango (1949)
The cast contains: Julio Martel - Graciela Lecube - Héctor Ferraro - María Esther Buschiazzo - Gloria Ramírez - Manolita Serra - Héctor Gagliardi - Osmar Maderna - Domingo Federico - Óscar Alemán - Juan Carlos Barbará. Text: Alfonso Gárgano.
The film is originally released in Argentina in the Spanish language in black and white and has a runtime of 70 minutes.
Thanks Jørgen to post this link in the comments of the
Oscar Aleman blogspot.