Kapoor's contribution was the (so)longest

The only female solo on the soundtrack of Dono was Khatt Mitthiyan – it was sung by Himani Kapoor.

It was the second song in the film that began with the letter Kh.

The song was written by Irshad Kamil.

Shankar Mahadevan, Ehsaan Noorani, and Loy Mendonsa composed it.

By the way, it was the longest of the seven songs from the film in my collection – it was four minutes and 37 seconds long.

In other words, the songs at both ends oxf the duration scale on the soundtrack of Dono began with the letter Kh.