Rayna tunes her bass down two and a half steps. The tuning is as followed (B, E, A, D) If you have a 
4 string I sugjest buying fatter strings so its easier to tune that low. She also uses a hipshot 
that shoots the B down to an A at times but its just for playing live.

Main Riff:

D |--------------------------|
A |--------------------7-----|
E |-7-78-77-8-77-8-7---------|
B |--------------------------|

Chorus:

D |--------------------|
A |--------------------|
E |--------------------|
B |-2--0-2--0-23-------|