How to determine the Key of a Song??

I have a doubt I mind, if any one can clarify. There is a Hindi song called musafir hoon yaro.. It starts on a C Major chord.. It has only 3 chords throughout, that are C Bb and f.. But Bb and C are the 4th and the 5th chords in the progression of F.. So is the Song in the key of C or is it in the key of F???

F, there is no Bb in the key of C major

A song doesn't have to start with the 1 chord. So, thats that. Key of F

thats a V IV I progression in F. its kind of common

Here's the link to the song.. I feel the Key is C dominant.. If any1 could confirm it for me.. Thnx in advance ... http://www.youtube.com/watch?v=wDWhRPu-eCM

You're sort of right... C Dominant just means it's the V (mixolydian) of the key - but it's still in the key of F Major. It's basically focusing on the V mode though :)

Jazz got there before me - I agree that it's in F, but that C chord is definitely more prominent as is the b7 that leads into it, all of which strongly points to C Mixolydian. Much of Hindi and Bhangra music uses modal key centres quite frequently, so it's nothing unusual.

Afro

The song is in the key of C ....... but its the 5 chord from F major. Which means , if you were going to solo over it, you would play C mixolydian( which is an F major scale but starting from the C ). So you could say the song is in the key of C dominant. C is the 5 chord, B flat major the 4 chord, and F major the 1 chord..... but it keeps going back to the C chord, making that home, making it in the key of C........

Why make a topic if you already know the answer?

I'm slowly gaining the impression you're copying your facts from somewhere...

Ofcourse I am!! And I had posted my question at a diffrnt forum aswell.. I got an answer from there. Thought it would help other people aswell, thats the reason I've posted it.. So the people who might want to share the info are most welcome...