I usually set a global variable so that when they return to the page, it remember's that they turned off the music.
I make a sprite button with two frames, 0=on & 1=off
the global variable hold the same values so the frame can be set with it when returning to the page.
I check the sprite for a touch and if the sprite is on frame 0 switch it to 1 and if it's a 1 switch it to 0. and set the global.
The common problem with buttons:
since the second event also sees the click, and the frame switched in the first event to 1, it will fire switching it right back to 0.
So, when the first event fires, wait 0 or .1 before setting the value, so that it will wait a tick before setting the value. The second event saw the value was still 0 and didn't fire. Then the value changes next tick.
(wait 0 waits until the next tick.)