>> The Issue is standalone-mode<<
Hello,
to make it short:
my Virus works fine in standalone-mode, EXCEPT my Mac boots and connects to the Virus-USB: then I loose my sound.
(I don't have any issues inside Cubase. Inside the Daw tone is back).
It looks like MacOS-USB and Virus-USB have a conflict!? (I went through the Mac Audio-Midi-setup...)
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following more detailed description/scenarios after upgrade to Mojave:
1. Inside my DAW (Cubase) Virus (Total Integration) is running fine - so far so good.
2. When my Mac is NOT switched on I can play Virus (TI keyboard) in standalone mode (correct wording?) - also fine.
==> 3. As soon as my Mac is booted in parallel I can play just ONE tone or chord on the virus (audible) - then the tone is gone, vanished!!?? 
(I use USB-connection from Virus to Mac)
No cables have been changed: The outputs of the virus go into my MACKIE 802, and from there to audio-interface MOTU M2.
Note: on another synth, which is midi-triggered by 5-pole connection (not USB-midi), MOTU output sound works perfectly fine as usual!
(while writing this for a 2nd time, I had a sudden system crash in between 
and had to reboot)
So what I want to get back: I want to play my Virus outside a DAW like before while Mac is running in parallel , of course .
I have no clue what the issue could be.
Virus firmware is on 5.1.7.00
The Virus Control Center doesn't offer me a newer version.
I looked at MOTU drivers for Mojave : "appears to be compatible" (although it is also said that MOTU M2 does not need any drivers on a Mac)
My Mac: Mac Mini end 2012
Looking forward to any suggestions from you.
Thank you very much!!
? No answers? Legacy Issue? It doesn't seem to be a real Virus issue? Is it more a general USB-handling problem? Mac Mini too old? But I love my AV 
Schreiben hier eigentlich alle auf englisch?