In theory--one theory, anyway--you want sound that excludes your tinnitus frequency. The idea is that cortical response to frequencies builds up according to exposure. This has never made a lot of sense to me, but neither do competing theories.
A number of treatments try to undo the presumed plasticity-related changes in cortical frequency-assignment by using sound spectra that might result in a lateral inhibitory effect on the "over-sensitive" neurons. This would reduce tinnitus, but I've never understood why it would (by that mechanism) result in a permanent change.
The vagus nerve stimulation approach is interesting, because it tries to do something to increase brain plasticity at the same time it uses a (pretty simplistic) sound retraining exposure. Maybe such an approach will eventually work when we have a better understanding of what the precise changes are in the auditory system with tinnitus and when we design a sound spectrum that would restore things to normal and combine it with a drug or something to increase plasticity.
But we aren't there yet in my opinion.