it works beautifully and way easier than I expected.
connected my otg cable and the phone said usb connector connected (since when is this a thing!?), plugged in the midi-usb adapter to the otg cable and right away it prompted me to open with the software I linked above and another midi software I had installed.
and bam, it was working. I messed around a bit to find the better settings for my keytar, but this thing works. over Bluetooth and with the headphone plug. there's a little bit of lag over Bluetooth but for my uses I wanted it straight to the speaker so i'm using the stereo cable. now I don't need a pc to get sound out of the keytar.
mark this as one more day i'm amazed at what my phone can do.
by the way, it functions as a synth using the software I mentioned above, so I can play harpsichord, organ, piano, etc. and the sound keeps on playing even with the screen off.
happy camper = me.