The answer to this is Aap ke Sewa Main. This is a song that was sung for a movie that was released in the year 1946. There are a lot of songs that were released in the past that are now easier to access online because people can now upload the songs through different video channels or other online applications.
Not everyone may be able to appreciate Hindi music but this is still one of the songs that you can listen to if you just want to get a glimpse of how Hindi music sounds like. There may be some changes that have occurred with this type of music over the years.