My music app content(not Apple's Music app) disappeared after I backed up and updated my phone to IOS 9.1. How can I get it back? When I try to download using the app, the app always crashes before it can complete.

My music app content (Not Apple's Music app) disappeared after I backed up my phone (Iphone 5S) and updated it to IOS 9.1. Is there anyway I can get the songs(content) back? The rests of the apps are fine. It's the first time I have backed it up onto my laptop-my second one since the first was stolen-, but the app has been there since my last iphone. Typing out a sincere plea for help because there are way too many songs to be re-downloaded again using another app.