> Vocals and music were recorded on separate tracks. Revival series used
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> original vocal with newer instruments.
>
> That also allowed practice of dubbing, where Didi would come and sing
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> and replace original singers voice.
Now I remember a radio program I heard years ago. It could be a special 'Jayamala' program on a Saturday (used to have some celebrity from Film Industry presenting for the soldiers) This fellow said that something was not quite right between Jaikishan and Lata so the song was recorded in the voice of Mubarak Begum (he used a word for dummy voice, I don't remember). It was 'Mujhko apne gale laga lo ai....' for the film Hamrahi. The idea was, later Lata would sing it. But the song was released and became a roaring hit. This terrified Jaikishan even more who just couldn't muster courage to face Lata. So the song was packages as it is for which Mubarak Begum got Rs 500/-
So this means we have all songs with separate vocals and Instrumental score from way back in sixties......