Some movies contain musical shows, that although they have a diegetic justification, interrupt the actual narrative flow. Those are the characteristics:

• auricularization 0: the sound realism is canceled in order to have the best sound quality (similar to a CD sound).
• it is absolute music and no other sound is heard. The sound is the same whatever the camera distance
• sound is recorded in studio with professional musicians and played back as a recording

Background versus show song in Beltenebros (Pilar Miró, 1991)

Iconic actress Rita Hayworth often appeared in musical shows with a diegetic justification in the films, like in Gilda (1946):
https://www.youtube.com/watch?v=e-LO9Ay6v_M

Sara Montiel, a Spanish actress best known for her singing also made movies with numerous musical show inserts:

Sara Montiel sings ‘Quizás, quizás quizás’ as a filmed show in Noches de Casablanca (1963).

Remake of the song with actor Gael Garcia Bernal from Almodovar’s movie Bad Education (2004). Almodóvar’s use of music often consists in using diegetic songs as musical shows that interrupt the narration.

Sara Montiel singing ‘fumando espero’ with a diegetic justification in El último cuplé (España 1957). 

Music show hallucination in Eli Stone 1×02

In classical music, there is also the use of musical shows using the best world orchestras and performers regardless of the plausible and realistic level of the characters in the story.

Musical show with Brahms’ first symphony played by an orchestra of students but a recording of the Berliner Philarmoniker in Nodame Cantabile 1×19.

Music examples in Iko shashvi mgalobeli

Iko shashvi mgalobeli (Iosselani 1972). In this film, the main character is a musician that plays at the orchestra (timpani) and combines with several musical activities in Tbilisi. There is a combination of realism with some musical show incursions.

Intervention of the orchestra (Die Walküre) at the beginning of Iko shashvi mgalobeli (Iosselani 1972). The sound is realistic and does not sound like a studio recording. There is no narrative pause for pure music listening sake.

Final of the first act of Die Walküre

Traditional polyphonic Georgian music. The sound seems a direct recording with the actual voices and technique of the actors. Combination of realism with a pause for listening the music.

Traditional polyphonic Georgian music in a diegetic realistic context. The sound seems a direct recording with the actual voices and technique of the actors. Combination of realism with a pause for listening the music.

Song accompanied by the piano in what sounds like a studio recording: more similar to a musical show where music appears for the audience pleasure rather than a narrative imperative.