Man there r alots of chords in the key of C. hmmmm yes. well I will tell u some C chords. theres ur basic three part harmony which is like C major (c,e,g) and C minor (c,Eb,g) and ur not so simple three part harmony (c,Eb,g) C sus4 (C,F,G) Csus2 (C,D,G) Cb5 (C,E,Gb) Cmb5 (C,Eb,Gb) Caug(C,E,G#) then theres four part harmony C7 (C,E,G,Bb) Cmajor7 (C,E,G,B), Cm7 (C,Eb,G,Bb) Cminor major 7 (C,Eb,G,B) C7aug (C,E,G#,Bb), Cdim (C,Eb,Gb,A), C6 (C,E,G,A) Cm7b5 (C,Eb,Gb,Bb) C2/Cadd2/Cadd9 (C,D,E,G) Cm2/etc (C,D,Eb,G) Cm6 (C,Eb,G,A) then u can go like Cadd 13 and what ever u want like #9 which just mean play C and add the #9 or what ever in c the #9 would be D# you just count and stuff its quite simiple once u got that hang of it, Then you got ur 5 part harmony and things start getting realy jazzy its great. C9 (C,E,G,Bb,D) Cmaj9 (C,E,G,B,D) Cm9 (C,Eb,G,Bb,D) C7b9 (C,E,G,Bb,Db) C7#9(C,E,G,Bb,D#), then things get realy exciting when u start geting into 13 and a 11th chords whichs r like 6 and 7 part harmony oh fun, but most of the time people mis out notes like on the guitar u cann't play 7 part harmony inless ur real talented and have a 7 string guitar which i would luv to c and its realy hard to play 6 part harmony on a guitar, a C11 is C,E,G,Bb,D,F people sometimes miss out the 3 in this or maby the tonic which is the C and let the bass play the c, You also and sharp and flaten things but a good way to look at this chord is 2 chords like a C and a Bb in this case it make life easy, then C13 is fun I luv 13 my fav chord but i miss out notes and play it as 5 part harmony, You can like mis out the 11 and the 9 bepending on the sound u want but the full C13 is C,E,G,Bb,D,F,A again u can sharpen and flat notes. You also can like take the C chord and just add notes like Cadd b6,#9,11 etc (i made that chord up i dont no wat it sounds like could be intresting for it to sound ok u would have to play it up high on a piano maby and like play with the inversions, you also have like poly chord when u play like more than one chord at a time like C and a D etc, well i might of missed some out but like thanks for that question cause u made me think even though i prolly didn't do wat u asked but meh i had fun that all the chord i no bassed of C basical i think but if u have any question yell out