Play podcast, audio book or song simultaneously on one device

[Patricearcand]

I need a sound mixer with Spotify...

As a Game Master, I would appreciate to play an ambient file (like a forest sounds, wind sounds, growl sounds) along with a music track to create a particular ambiance. I would like to do the same with podcast or audiobook as I like to have some music and or sounds  mixed to it to create also a suitable atmosphere.

This would mean that not only could  start multiple tracks at the same time but also that I could choose the volume of each track as well as easily remove or add sounds to an ongoing mix.

It would also be important to be able to save this mix with set sound levels for reuse later or to let the community use it.