Of course, Lata Mangeshkar. It is not without reason that she is called 'The Nightingale of India". I haven't heard any female singer sing sweeter than Lata ji. Of course, listen to some of her songs under Madan Mohan like Zara Si Aahat, Lag Ja Gale Se, Naina Barse Rimjhim Rimjhim, Mera Saaya etc. and you would know what a heavenly experience is. The voice of Lata Ji in these songs is unparalleled and that if you close your eyes and listen to them you will feel that you are lost in a world of sweetness and melody that could only be created by Lata Mangeshkar.
Lata ji's voice had tremendous innocence and that is what made her suitable for most types of songs and for most of the actresses. If you can, I would advice you to listen to the song from film SHAHEED- Hum to Lut Gaye Tere Pyar mein , and just be amazed by the sweetness and innocence in the rendition of the song. If you want I can put it up here on the forum.
Legendrafi ji, I'll love to have the number from Shaheed if you have it in good quality. I have it but quality is so so.