Hi everybody,
for me it works too on 10.13.6 High Sierra (Hackintosh)!
First I got double messages via MIDI from V-Synth USB.
I installed the latest Roland-UMOneUSBDriver (MK2) over the patched V-Synth-Driver . Now it seems to work but I didn't testet audio-device function. Maybe there's need to change Settings in V-Synth Prefpane
What i did:
download latest V-Synth GT USB Driver v1.0.0 for Mac OS 10.8 from
https://www.roland.com/global/support/by_product/v-synth_gt/updates_drivers/
Remove system version check in installer with
PackageMaker.app from Apples Developer Site (search for Auxillary Tools for Xcode - Late July 2012.dmg )
Builded the package and install - reboot and V-Synth appears in Audio-MIDI-Setup
but it sends all notes twice.
Now I installed the UM-ONE mk2 Driver Ver.1.0.2 for macOS 10.13 / 10.14
https://www.roland.com/global/support/by_product/um-one_mk2/updates_drivers/
reboot and both MIDI interfaces works
Please be shure to have a real working backup before installing not supported drivers !
BTW:
I'll never more buy any device from Roland.
I spended a lot of money for a top-synth but Roland dont want to support an easy to write USB-Driver for good customers. That's very poor for sutch a company. V-Synth is not the only one device from Roland without driver support after couple of years. Yamaha even supports my old Motif 6 on latest Win / macOS