mels, if you want to pass through the audio from an HDMI input to the HDMI output, make sure to read page 89 of your manual.
Set the HDMI parameter in Setting the Audio options on page 88 to THROUGH if you want to hear HDMI audio output from your TV or flat panel TV (no sound will be heard from this receiver).
It may not be quite the "standby" you want, but at least it may achieve the goal you seem to want (audio coming from the TV).
For the Standby to work, according to the manual (page 85), both the TV and the source must support "Kuro Link", which is Pioneer's name for HDMI CEC
. See the third paragraph in that link for all the various manufacturer's names for it.
When the receiver’s KURO LINK is turned ON, even if the receiver’s power is in the standby mode, it is possible to output the audio and video signals from a player via HDMI to the TV without producing sound from the receiver, but only when a KURO LINK compatible component (Blu-ray disc player, etc.) and compatible TV are connected. In this case, the receiver’s power turns on and the power and HDMI indicators light.
It might or might not work with other manufacturer's component.
Hope this helps a little!