This app lets you control your Harman Kardon AVR through your smartphone.
Please be aware that this is not the official Harman Kardon AVR app, but with this Remote Control app, you are enabled to control it.

Our app comes with a wide variety of remotes, so you can choose the one that best fits your device.

The app allows you to use your harman kardon AVR even if you cannot find the remote control! However, the app requires your phone to have an infrared sensor.