94 wagon, GM radio with equalizer and cassette half way died

Never seen it so weird, like radio controls, some of the buttons change the display, but has no sound. Can not change channels except with buttons, and no scan. Turn volume up and display changes, but has no sound. I had parked car for 2 years. Started it up, and radio came on, sounded like just one speaker was working, but volume could not adjust, turn it off, still playing sound. Radio is OFF, and it is playing the station.

Kept pushing buttons, turned off car, buttons changing display but no sound at all.
Any ideas on how to fix it? It worked fine before I parked it.

IT has  fixed itself. It has been really humid. And now cooler and drier outside, I left the driver window down for couple days. Just now, I tried it and radio is working perfectly. I also hear what sounds like a relay click when I turn it on, so maybe there is a power relay inside the radio that was stuck or not making a good connection.

This wagon has the 'premium sound system' what ever that means. And IMO, radio always sounds good.