Often the question has been asked here, if there's any way make an Arduino board appear as a USB audio device.
This is now working on Teensy 3.x, at least in early alpha testing. Here's the conversation, which has links to the code and other info needed to use it:
It's been confirmed working on Mac, Linux and Windows, and partially with iOS & Android.
Today all the code is only on github, so you have to download files and copy them into your arduino folder in the right place. Minor edits in boards.txt are needed to get Audio to appear in the Tools menu. USB doesn't yet appear in the audio design tool, so you have to manually edit your sketch code to add the AudioInputUSB and/or AudioOutputI2S objects which provide the real-time streaming sound. Probably not for the faint of heart to use at this early stage, but all the code is there for anyone wishing to do things a bit manually to give it a try.
In a few weeks I'll publish a beta version with a full Teensyduino installer and updated design tool, to make it super easy.
Many people have asked for this feature, especially within the last year or so... and now, here it is! I hope you find it useful. 