I'm assuming you're playing guitar. If so, play a C7 but up two frets. Or play D7 and play the top E string open. Basically a 9 chord is the root, 3rd, 5th, 7th and 9th (ie root + one), so D9 is D F# A C E (but not necessarily in that order. There are loads of chords sites on the interweb thingy. Google "guitar chords" or whatever instrument.

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