Mute and unmute music once it’s started playing in Adobe Animate

I’m trying to create a game that demonstrates the different instruments in a band. I’ve managed it in AS3, but I’m struggling in Javascript.
You can either listen to all the instruments playing a piece of music, or click on an instrument to enable or disable it, thus bringing it in or taking it out of the mix.
I have 8 tracks that play simultaneously when the play button (play_btn) is pressed. But whether each instument plays or is muted depends on whether another button (e.g. congas_btn) is pressed. If it isn’t pressed, the conga player, for example, (congaPlayer_mc) is greyed out and the conga audio track is muted. If it is pressed, the conga player has full alpha and is unmuted.
Each instrument should be able to be muted or unmuted at will whilst the track is playing.
What actually happens is that whichever state I choose (muted or unmuted) before I click play, determines whether the track plays muted or unmuted. But once the track has started, the congas_btn doesn’t have any more effect on the volume. It just toggles its alpha value.
How do I get it to carry on affecting the volume for as long as the track is playing?

Thanks.

This is my code:

let root = this

let congasActive = false
let audioPlaying = false

this.congaPlayer_mc.alpha = 0.5

this.play_btn.addEventListener("click", playAudio.bind(this))

function playAudio() {
    
    const playCongas = createjs.Sound.play("congas")
    
    if(!audioPlaying){
        
        audioPlaying = true

        if(congasActive){
            playCongas.volume = 1
        } else {
            playCongas.volume = 0
        }
    
    } else {
    
    audioPlaying = false
    
    const stopCongas = createjs.Sound.stop("congas")
        
    }
    
}

this.congas_btn.addEventListener("click", activateCongas.bind(this))

function activateCongas() {
    
    if(!congasActive){

        congasActive = true
        root.congaPlayer_mc.alpha = 1

    } else {

        congasActive = false
        root.congaPlayer_mc.alpha = 0.5

    }
    
}