Question 1: “Does anyone know if RealVNC, TightVNC, etc... will allow audio pass through? For example, to allow sounds generated by the host computer to reach the remote computers that are logged into the desktop?”
Question 2: “Does anyone know why an RDP session would be dropped anytime I have a VNC session connected? We run RDP on a large monitor 24/7, but occasionally need to have 1-2 client PCs connect via VNC to view the desktop, but the RDP session drops anytime we connect.”
1) VNC does not transmit audio.
2) I'm going to assume that you're trying to open RDC and VNC sessions to the same computer at the same time. I'm also going to assume that it's an RDC session to the "console" rather than to a terminal server.
When you connect via VNC, the OS sees that as the same thing as someone using the connected keyboard and mouse. Windows doesn't allow an RDP session and a console session at the same time, except with Remote Assistance or a terminal server. If you log into one while the other is active, the other gets disconnected. This is just the way RDP licensing works with non-server versions of Windows.
