Orpheus is a FireWire multi-channel audio interface, and can be used as an 8-input 8-output mixer.
Since we want to compare the sounds form IC-7410 and Soft66LC4 both receiving the same RF signal, we put the analogue sound output of IC-7410 into AI5/AI6, and HDSDR output into AO 1/2.
You can mix and monitor the sound using the Control Panel of Orpheus. A solo button is a quick way to listen to a particular source only.