If you have a start button to play the movieclips I would not even put the sound oon the movie timeline.
Since you have a linkage name here is what I would use on the click event. I would put that in Frame 1 of main timeline. then you can use the variable to control the sound like
this.SPsound2.paused = true;
var root = this;
this.startBtn.addEventListener("click", startSound.bind(this));
function startSound() {
root.movieclip.gotoAndPlay(framename or number); // or whatever you want
this.SPsound2= createjs.Sound.play("SPsound2", "none", 0, 0, -1, 0.4);
// play ( src [interrupt="none"|options] [delay=0] [offset=0] [loop=0] [volume=1] [pan=0] [startTime=null] [duration=null] )
// here I set loop to -1 which means it is looping
}
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