Specifically, I've tested my unit against five of my USB-MIDI controllers, and four of them cause the LED display to flash a reassuring "don" (i.e. "device on") when plugged in, and produce the appropriate sounds when played

The unit worked as expected, as a compact sound engine for my USB keyboard

Bottom line is that my Midiplus really shines as a simple portable self contained mobile practice midi engine and keyboard power source for my piano practice when combined with an excellent portable sound-less keyboard like Xkey

The sounds aren't amazing or anything, but c'mon, for the price, this little device turns a MIDI controller into a 128 instrument synth!

(the drum pads play the appropriate percussion sounds when tapped; astonishingly, the midiEngine was able to power the entire keyboard without the AC adapter, though I'd probably plug in the latter anyway so as not to drain the module too quickly