Streaming Audio through the Radio

I just did something I should have done a while ago.  My local
favorite talk show (NYC) is pre-empted by hockey...so I am streaming
97.1 St Louis from the computer audio out to the phono jack in the
back of my 1939 RCA 5Q55.
Sounds great!  One thing is different.  The volume is controlled by
the computer, not the radio.  Once it senses audio on the jack, it
switches over to the computer muting the radio.  I don't even have to
unplug the jack.  Most of you folks are probably used to this, but it
is new to me.
Boy, I love these old radios!

Mike
Walden, NY