Wow!, that was fast decoding. Yes, video clips are superimposed on audio. As you said, video clips are from the song "Aap Yun Hi Agar Humse Milte Rahen".
The more I find about this song, more fascinating it gets.
A corrected version, someone has posted by assembling the original soundtrack (audio only) with proper sequencing.
https://www.youtube.com/watch?v=YrvH9Hc7aaMWith proper sequencing, its amazing, how much better this song becomes. Excellent verses and replies. Romantic song, but without mentioning 'I Love You' and a totally innocent song and still romantic.
Moreover this sure is the title song. Mentions 'Ek Musafir/ and also Hasina (Nazneen, Mahzabin).
As the producers were in a hurry to let the announced screenigs to go on,I wish, the producers had left the incorrect version or at least put partial song, until the error.
Although the producers did find out about the error at the time of its release (more than 60 Yrs ago), and hid the error by not including the song in the film, it's only now that it has come out. Such a popular song and no one noticed. Even until 3 Yrs ago, in the stage shows, they always sang the incorrect version as no one noticed the error. It's only now, new postings of any stage show with this song, corrected version of this song is sung.
I can think of another duet with excellent verses and replies, Tere Pyaar Ka Aasra Chaahta Hoon'. But that one too pales against this 'Main Pyar Ka Rahi Hoon' corrected version.
Another tid bit about this song:Song was recorded when some musicians were on strike or did not reach the studio, so was recorded with minimal music.You can find a revival version of this song on youtube that has more musical instruments (Mainly Tabla) as perhaps was intended. But, surprise is that the original corrected version, with limited musical instruments, still is lot better. Adding extra musical instruments made this song less sweet.