to support sound from more than one application at a time you must use a sound server, for KDE this is aRts. Set up to use arts in the sound section of KDE control centre, be sure to also set Konqueror->settings->configure konqueror->plugins->netscape plugins window/plugins tab 'use artsdsp to pipe plugins through aRts' checkbox to 'yes'. You will also have to install xmms-arts plugin & configure xmms to output to it. Other multimedia applications may need similar plugins.