Sophia The 3 bars, F7 C7 C7 are the simple body of the tune. The 2 bars below are to be substituted for the last 2 bars of C7, a classic ending phrase. If you play those triplets over a C7 chord however, it sounds terrible. Fine, with just the bass notes. The phrase implies a chord progression, and to actually see the tonality play, C7 under the first triplet, F#dim7 over the second, Fm6 over the third, then C, F, F#, G in the last bar, before returning to the top, or playing a final ending chord, which could be a simple Cmajor triad, or C9 for a more jazzy sound.
