via this auction
"This box can implement microtuning capabilities to most midi synths that respond to pitch bend cc’s. It works best with multitimbral synths or those that have Mode 4 (guitar mode, mks50, esq-m) for polyphonic use but can work for monophonic synths too. It has over 400 tunings included but you can upload your own from a computer. I highly recommend getting HPI’s Custom Scale Editor software if you pick this up as its easier and more intuitive than Scala for creating your own scales. Comes with original power supply.
