When I first purchased the VL3D I found it worked well with two of my Roland keyboards through the Midi channel but did not function with my Roland KF90 digital piano, however I found that it did work when plugged in from the line out socket on the keyboard with the normal jack lead going into the guitar channel perfectly. I haven't found out why it works this way but 'if it ain't broke don't fix it'. Lovely piece of equipment. I now use it regularly during live performances.
I mainly bought the Digitech Vocalist Live 3D Desktop Vocal Harmoniser for just tweaking my mic, give my microphone a bit of reverb, compression, Noise gate and warmth, the harmoniser bit on it is a lot of fun, but I would of bought this unit even if it had not got the harmoniser, so look at the harmoniser as a bonus.
This device is really well designed. Very solid box and at first look makes good impression indeed. I bought Digitech Vocalist Live 3D Desktop Vocal Harmoniser tempted by "Vocal" term, but unfortunately my vocal sounds much worse than I expected. There are 3 reverbs and none of them is deep enough and without delay effect this device is just useless to me. I did not make any tests with instruments so thats why 3 stars but was considering to give 2.