"Country Tuning" is one of the simplest altered tunings. You raise the 5 Draw by one semitone.
Using the Grobet 0-cut file and a good reed support tool, this can be done in a minute or two.
You get a major seventh instead of a minor seventh. If you use the 12345 draw chord, it's now a Jazzy-sounding major seventh chord.
The 456 draw chord is now a major chord, too! On a standard tuned Richter harp, that's a minor chord.
This tuning also enables a draw bend on the 5 Draw reed.