Some of the backing tracks set from iTunes, their volume fluctuates. Why is this and how can we prevent it?
Different tracks may have been mastered at different levels. It happens but there isn't anything we can do to prevent this. Apple now has a setting called Sound Check that when it's turned on, it will go through your music and neutralize everything to be on the same level. This can be turned on in your devices settings app > Music > Sound Check, turn on and you should be set to go from there.