Hi,

I am not really sure what you are asking here.  Are you saying that the strings that you want to use are played in the key of C and you are having trouble figuring out what guitar chords need to be played in that key to match the music?  Strings (violin, cello, etc) typically do not play chords the way you play them on a guitar, they play notes that are part of a specific key.

If this is your question you can either change the pitch of the instruments you have selected for your project, or change how your guitar is tuned using alternate tuning instead of standard tuning or you can use a capo to play in pretty much any key you want to.

Personally I usually don't worry about what key other instruments are playing in, I just adapt the chords or notes that I play to that key.  However, sometimes fingering chords becomes a little challenging, so for those situations I do us a capo.

My personal approach works best for people who play by ear and do not rely on sheet music to play music.  People who play by ear rely on experience and knowing chords and chords/note progressions while people who play using sheet music are basically in deep trouble if the music on the page has not been transcribed to the key for their instrument.

Good Luck,

George