"If the input for ZONE2 is set to “Source”, all types of input signals can be listened to from ZONE2. link
If the input for ZONE2 is set to a specific source (like CBL/SAT), only analog signal or 2-channel PCM signal input (from HDMI connectors or digital connectors (OPTICAL/COAXIAL)) can be listened to from ZONE2. To playback HDMI signal other than 2-channel PCM in ZONE2, set “HDMI Audio” to “PCM”. link 2-channel PCM signals are output from a device connected to the input source selected for ZONE2 and can be played back in ZONE2. In this case, the MAIN ZONE audio will also be converted to 2-channel PCM signals if the MAIN ZONE and ZONE2 are set to the same input source. However, depending on the playback device, the playback signal may not be converted to PCM even if this setting is configured."
While the NR1711 does have a zone 2 and it can pass audio from HDMI through, it must be the same source as what's playing in the main zone.
From the NR1711 manual:
"If the input for ZONE2 is set to “Source”, both digital and analog connected devices can be listened to from ZONE2." (I think this would be closest to the Yamaha party-mode feature you mentioned.)
"If the input for ZONE2 is set to a specific source (like CBL/SAT), only connected analog devices can be listened to from ZONE2."
