I have one set up with 4 equal distance strings. I'm a more traditonal style player and play with a lot more droning than many who play with that configuration. I find it a good configuration for bagpipe tunes since one can play the melody on one string and have droning high and low. My strings are usually DDAD. If cross picking, it is tantamount to a three string configuration and I don't see much advantage. However, some tune the extra melody string to a different note which essentially makes a chromatic dulcimer--then strumming on all strings at the same time becomes a little trickier. I occasionally tune the four strings to DADA. Again when playing bagpipe tunes, it allows for two octave droning and simple chording using the first set of DA is pretty easy. Of course, the problem is that you have three drones and only one melody string and it tends to get drowned out. I have really just experimented with it and don't use this configuration on a regular basis. The dulcimer is such a quiet instrument when playing in jams without amplification that I usually need all the melody I can get AND this configuration usually doesn't fit my style as well as more typical arrangements do.