Keyboards basic question

Hi, The sheet music for songs has this indication: key: C (sometimes Cm, D, A etc)
what does that mean ?
Iam assuming just like we play scales, where we place our starting finger on that key. Example if the song says play in the key of C, then i should position my hand such that the thumb is on C. Lets say , if the song is to be played in the key of A, then i should place my thumb on A (atleast have the finger positioned that way to start with). Is that correct?

 

if you're playing off sheet music, then knowing the key doesn't really assist with the playing or reading of the music to any great extent. If you're improvising, then knowing the key is essential of course.

 

I'm not sure what type of "keyboard" you are referring to. The answer differs a bit depending on the type of keyboard.

For a piano, when you are playing from a piece of sheet music, your hands are assumed to generally start in the same position always (right thumb on the middle C, etc., as one is taught). If your hands need to be positioned somewhere else, the sheet music will generally clearly indicate that, but it's not the norm at all.

The "key" indication for a piece of piano music just gives you an idea of what notes and chords to expect, and also giving the key allows other voices and instruments that are key-dependent to tune themselves to play along with you. It doesn't indicate that the pianist moves her hands to a starting position to match that key.

You would only move your hand to a new position if you wanted to sight-transpose the key of the sheet music, i.e. the key is C and you want to play the piece in G. The easy way to transpose C to G would be to move your hands from the starting C position to the G position and play the notes on the sheet in the new position. Since the piano player would have to be cognizant of changes in sharps and flats when moving to the new key, this is a fairly advanced activity and usually done by people such as professional piano accompanists who can play a particular well-known song in any key that the singer asks for.

For other types of keyboards, such as electronic ones, the key indication might suggest settings that you have to make on the keyboard, such as pressing a button to set a particular key. This varies by type of instrument and since I mostly played piano I'm not an expert on that.

I hope this helps.