You can create a text called "music1"(text object), other called "music2" (text object)etc, then place "music1" in layout1 "music2" where you want.(make them invisible)
layout1
"music1"(text) is on screen-play music A
trigger once
layout2
"music2"(text) is on screen-play music B
trigger once
that way you can switch musics by switching textobjects between layouts.