Yes you can put more than 1 piece of custom music.
Have a look at this. There are 3 custom musics.
class CfgMusic
{
tracks[]={ Music1, Music2,Muse};
class Music1
{
name="My music1";
sound[]={"\music\intro.ogg",db+40,1.0};
};
class Music2
{
name="My music2";
sound[]={"\music\barrabarra2.ogg",db+40,1.0};
};
class Muse
{
name="muse";
sound[]={"\music\muse.ogg",db+40,1.0};
};
};