Music in the Film BV Social Club?

The "Trio" that sings "Domitila" is certainly cuban, but it is not identified, according to imdb, the background music is played and writen by the welsh duo Frank and Laurence Deniz.
elmasemlio

The music breaks down into two streams: (1) the repeated use of the street trio's song when they are following Hawthorne and Wormold, and (2) the background guitar music which changes in character and tempo according to the action. It's number 2 which is of real interest, because, in the way the cinematography and the music are combined to create the atmosphere of each scene, it almost exactly replicates the way Reed used these two elements in his thriller, "The Third Man", set in Vienna and made ten years earlier than "Our Man in Havana". In the earlier film the music was played on a zither, but soft zither melodies resemble the soft guitar melodies very closely (they're both plucked strings). Some of the replications are almost exact. For example, in "The Third Man" there is a scene where the character Holly is chasing Harry Lime through streets at night, with strong shadows cast by lamps and windows, and when Harry disappears into an apparently empty square, the zither hits a series of strong, low-register chords. In "Our Man in Havana" the same type of chase is involved in the scene where Wormold temporarily loses sight of Carter in the shadows of a street arcade due to the passage of a car, and the guitars do exactly the same thing -- a series of "low" chords. There are many other similarities of the later film to the former, although the actors are more "low-key" and the pacing is a little slower (perfectly appropriate for hot and humid Havana compared to Vienna in winter!). The zither player who supplied the music for the older movie was named Anton Karas, and the movie "made" him for several years as a cafe performer in Vienna. Unfortunately I don't know who plays the guitar(s) in "Our Man in Havana", but it's great film music.

In the opening credits is says "Music played by Frank and Laurence Deniz" but nothing more.

I am sure that the singer of the street trio is Luisito Pla of Trio Luisito Pla a very popular trio of the late 1950s in Cuba, I have many of their songs and the lead singer's voices on records and in the film are identical. It is possible they just used that group or Mr Pla to voice the song Domitila, a popular song still being recorded and perfromed in Cuba and wherever Cuban music is performed by musicians. It is also possible that it is Luisito Pla portraying the street trio singer

The reason that the music heard in the film including the conga heard in the adult club towards the end sounds like Buena Vista Social Club is because the BVSC played traditional 1940s and 1950s music and all of the older members of the group were part of the 1950s music scene in Havana