Music buttons - clicking on another music button will stop the music from the one you pressed before

you can always use SoundMixer.stopAllSounds() to stop all currently playing sounds, though it's often better to use a variable to reference the last played soundchannel and stop it explicitly when playing a new sound.  eg,

var currentSoundChannel;

function button1F(e:MouseEvent):void{

stopCurrentSoundF();

var s1:Sound1 = new Sound1();

currentSoundChannel = s1.play();

}

function button2F(e:MouseEvent):void{

stopCurrentSoundF();

var s2:Sound2 = new Sound2();

currentSoundChannel = s2.play();

}

etc...

function stopCurrentSoundF():void{

if(currentSoundChannel){

currentSoundChannel.stop();

}

}