Why do I have to activate Midi Thru to hear my VSTs?

Hi Cubase Experts,

I have an issue with regard to Midi-Thru. I use a Yamaha Clavinova CLP-585 per USB and a Roland Quad-Capture UA-55 per USB as an audio interface. In Cubase as well as in Dorico I have to activate Midi-Thru otherwise I get no sound from my VSTs. Since I have a latency problem in Dorico, I would like to find out if it is the midi thru issue.
Why do I have to activate Midi-Thru at all?

If I deactivate Midi Thru in Dorico/Cubase, Dorico/Cubase still shows me that it is receiving farther Midi data, but I hear e.g. from HalionSonic no sound.

Thanks for your answers.


It’s very well explained in the Operation Manual.