Watch the Swampy Trem online guitar lesson by Jeff McErlain from Guitar Effects Survival Guide
Tremolo can add a really cool swampy vibe to a tune, in this case I am mixing in some delay and reverb. A great example of this is on Buddy Miller's "Dirty Water". If you are not familiar with Buddy Miller, please check him out. He is a great player and singer and Emmylou Harris and Robert Plant's first call guitar player. What I love about him is that he can set a mood so easily with a few effects. On a fun creative note, really experiment with the tremolo speed and depth, slight changes in either can make a big difference.