I have made a similar tutorial for 360

To play music on your xbox, you need to download Jamcast.
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Once you have Jamcast downloaded,
1. On your computer go to Pandora or spotify and play music
2.Then go to windows media player and find other libraries, under that you will see jamcast, click that
3.In jamcast find playlists,click it, and then find and click virtual sound card.
4. Now here is where is might get kinda confusing, you need to find a random song "not in the jamcast library" and right click it and select play to and select xbox one."it will show it loading on your xbox"
A window will pop up showing that its loading the song
and starting to stream it to your xbox, now once that is done go back to windows media player and click and drag virtual sound card"not the playlist virtual sound card but the one inside it" into that pop up window. Click the right arrow to skip the song that you where playing to get that pop up window, and now it should start to play the virtual sound card.
If it doesn't start to play the virtual sound card make sure that pandora or stopify is playing
If you need help with this or need me to explain some of it more clearly, please ask.

To prevent audio from playing from the computer, mute your computers volume.

This works with any music thats playing on your computer whether it from pandora, spotify, or your own that you have saved.