A silent music app? – Polyphonic! Review

I just downloaded this app and when I try to use it I can't hear anything despite my phones volume being turned all the way up. I know my phone isn't the issue because sound on other apps works just fine. I tried deleting and redownloading. I made sure my phone's was not switched to silent. I'm using an iPhone 6s Plus.
Review by catchupcat on Polyphonic!.