Ask HN: Audio from two apps at once on iPhone possible?

I have rather debilitating tinnitus and sometimes am able to 'relieve' it by listening to various masking noises I find online that I download and mix. I would like to be able to listen to those tracks while also listening to other audio apps on my phone simultaneously (e.g. white noise and a radio channel) but iOS does not seem to support this functionality. When you start playing audio on an app, it mutes all other apps. I know it's possible to create an ios app to play two sounds simultaneously, but that would severely limit my ability to choose what to listen to (vs being able to listen to anything randomly on youtube or a radio app while also listening to the white noise). Outside of using external audio mixing hardware, does anybody know if this is something that is even possible to be developed in an iOS app? Essentially, the app would allow me to upload a bunch of white noise tracks, but would not mute once I fired up itunes or other audio apps. If not, what about android?