Hello David Walker,
Thank you for posting and the questions.
You can stream any content that you have from your mobile device that is not supported by SoundTouch by using Bluetooth. The only way a music library can be added to the source list in your SoundTouch app is by a computer or a DLNA compatible NAS drive like the WD My Cloud personal cloud storage.
If you have any other questions, let me know.
Joel - Community Support