If your AVR is the Sony STR-DN1050, then you should be able to network stream the music files on your LG G3 smartphone to it, via UPnP/DLNA, so no need to plug your phone into the AVR.
You just need to install a UPnP/DLNA media server & controller app on the Android phone, eg the free version of the excellent BubbleUPnP app. You also need to make sure your AVR is connected to your network, either wired ethernet or by WiFi, as it supports both. So long as the music files' music category data tags have been set properly (eg artist, album, track no, etc) you shouldn't need to worry about the physical folder structure that they're actually stored in, since the media server will automatically build the music library from the tag info.
Have you tried any of this before?
Last edited by Cebolla; 07-05-2015 at 01:57 PM.