If you are in C, the dominant seventh is G7.

But, a common device for a bridge is to modulate to C7, which is the dominant of F, so modulate the bridge to F from there, and to get back to C, use a G7, or Dm7 - G7 to cadence back to C. In harmony, a "cadence" progression is one the establishes a key, which is the dominant, or the supertonic followed by the dominant. So, if you were in C and played C7 ( the V of F ) or Gm7 - C7 ( ii - V of F ) you'd be modulating to the key of F, and the cadence chords cause the ear to anticipate the key change. A good example of this was done by Willie Nelson on his classic song, "Crazy".

That being said, I don't write songs based on "chords", which is a bottom up approach. I, or I try to use a top down approach, i.e., I write a melody, and the melody, if it is a good one, articulates the harmony. However, sometimes, if I'm stumped for a bridge melody, which is a new melody, in truth, sometimes relying on devices can help you get there. So, build up a repetoire of devices and a good way to do that to study how others have done it, so learning a bunch of hit songs of the past is a good thing to do and will help you write better songs. No, I'm not implying infringing, remember, chords are like water, they are a physical resource that no one owns, which is why they can't be copyrighted.

Last edited by pathardy; 01/23/12 10:44 PM.