how can i edit music in my iphone 6s

My daughter is a dancer. I am trying to find an app that actually lets me cut and splice 2 songs together which I have purchased on my iTunes the result of which is to be used on my phone with the music I own. I keep finding and downloading apps that supposedly do that only to find out that they do not. So frustrating. If this is not something I am able to do then I would like to know so I can quit wasting my time downloading worthless apps. I have an iPhone 6S Plus