I’ve been noticing steam messages seem to seriously reduce the audio of my music player and youtube videos and what not. It was a bit frustrating, so I searched for it and found a typical tech thread here. This didn’t help at all, so I carried on hunting and found the answer burief in steam’s forums, it’s a Windows setting which makes other things quiet when you’re “in a voice call” (which.. well, steam messages don’t really fall into that category). Anyway, file a bug report with steam if this irritates you, and find a workaround/fix here:
http://makingwindowseasy.com/2011/04/30/change-windows-volume-during-phone-calls/
It fixes the issue, and I’m pretty happy to mute my music when I skype or whatnot…
Bomadeno.com 