Some players like that Ennio Moricone music we can hear on server .

For those who don't like it , there is a simple solution to disable it. It just disables the background music , others sounds are still activated

I still use Windows 7 :  Go to PROGRAM FILES => ACTIVISION => CALL OF DUTY 4 - MODERN WARFARE => MILES => rename file MSSMP3.ASI in MSSMP3.BAK

Start game , music is disabled.

If you want to re-activate the music, rename again MSSMP3.BAK in MSSMP3.ASI

Very nice info Seawolf thanks.